ON THE TELEGRAPHIC DETERMINATIONS OF LONGITUDE BY THE BUREAU OF NAVIGATION.

BY LIEUT. J. A. NORRIS, U. S. N.

The following definitions are given by Chauvenet in his Spherical and Practical Astronomy.

"The longitude of a point on the earth's surface is the angle at the Pole included between the meridian of that point and some assumed first meridian. The difference of longitude between any two points is the angle included between their meridians." To describe the practical methods of obtaining this difference or angle, by means of the electric telegraph both overland and submarine, and especially those employed by the expeditions sent out by the Navy department, is the object of this paper.

Before the invention of the telegraph various methods more or less accurate in their results were employed, and are still in use where the telegraph is not available. The one most used and giving the best results was that in which a number of chronometers were transported back and forth between two places the difference of whose longitudes was required. "For," as the author quoted above says, "the determination of an absolute longitude from the first meridian or of a difference of longitude in general, resolves itself into the determination of the difference of the time reckoned at the two meridians at the same absolute instant." If a chronometer be regulated to the time at any place A, and then transported to a second place B, and the local time at B, be determined at any instant, and at that instant the time at A, as shown by the chronometer is noted, the difference of the times is at once known, and that is the difference of longitude required. The principal objection to this plan is that the best chronometers vary. If the variations were constant and regular, and the chronometer always gained or lost a fixed amount for the same interval of time, this objection would disappear. But the variation is not constant, the rate of gain or loss, even in the best instruments, changes from time to time from various causes. Some of these causes may be discovered and allowed for in a measure, others are accidental and unknown. Of the former class are variations due to changes of temperature. At the Naval Observatory, chronometers are rated at different temperatures, and the changes due thereto are noted, and serve to a great extent as a guide in their use. But the transportation of a chronometer, even when done with great care is liable to cause sudden changes in its indications, and of course in carrying it long distances, numerous shocks of greater or less violence are unavoidable. Still, chronometric measurements, when well carried out with a number of chronometers and skilled observers have been very successful. Among notable expeditions of this sort was that undertaken in 1843, by Struve between Pulkova and Altona, in which eighty-one chronometers were employed and nine voyages made from Pulkova to Altona and eight the other way. The results from thirteen of the chronometers were rejected as being discordant, and the deduced longitude was made to depend on the remaining 68. The result thus obtained differs from the latest determination by 0^s.2.

The U. S. Coast Survey instituted chronometric expeditions between Cambridge, Mass., and Liverpool, England, in the years 1849, '50, '51 and '55. The probable error of the results of six voyages, three in each direction, in 1855 was 0^s.19, fifty chronometers being carried.

Among other methods of determining differences of time may be mentioned the observation of certain celestial phenomena, which are visible at the same absolute instant by observers in various parts of the globe, such as the instant of the beginning or end of an eclipse of the moon, the eclipses of Jupiter's satellites by the shadow of the planet, the bursting of a meteor, and the appearance or disappearance of a shooting star. The difficulty of identifying these last mentioned objects and the impossibility of foretelling their occurrence prevents the extended use of this method.

Terrestrial signals may be used and among these can be included those sent by the electric telegraph. But when two stations are near together a signal may be made at either or at an intermediate station, which can be observed at both, the time may be noted at each of the stations and the difference found directly. These signals may be made by flashes of gunpowder, or the appearance and disappearance of a strong light, or a pre-concerted movement of any object easily seen. The heliotrope reflecting the image of the sun from one station to the other with an arrangement for suddenly eclipsing it, is a useful and efficient apparatus.

Various truly astronomical methods have been employed with good results, of these may be mentioned moon-culminations, azimuths of the moon, lunar distances, etc.

Coming now to the use of the electric telegraph for this purpose the following is a rough outline of the methods employed. Suppose two stations A and B connected by wire, and provided with clocks, chronographs and transit instruments. A list of suitable fixed stars is compiled and each observer furnished with a copy. The observer at A the eastern station, selects a star from his list and sets his transit instrument upon it. He is furnished with a key by which he can send telegraphic signals over the line and also mark the time on his own chronograph. The instant he observes the star crossing the spider line which represents the meridian, he taps his key, thus registering the time on his own chronograph and on that at station B and this operation he repeats with as many stars as necessary. B has his instrument set for the first star, and when it crosses his meridian, he taps his key marking the time on his own chronograph and also on A's. Then, disregarding instrumental and personal errors and the rate of the clock, A has a record of the times at which the star passed both meridians. The difference of these times is the difference of longitude sought, except for an error due to the time occupied in the transmission of the signal over the wire between the stations. B also has a record of the same difference of time with the same error affecting it in the opposite way. A mean of these two differences, will be the true difference with the error of transmission eliminated. This method has the advantage of not depending upon the computed position of the star. The instrumental errors may be allowed for, as well as the rate of the clocks, and the personal error may be eliminated by the exchange of stations.

There are disadvantages inseparable from this method, however, especially when the meridian distance is great. A star observed at the first station, may be obscured by clouds at the time of its meridian passage at the second. And the weather generally, at the two stations may be cloudy, so that while stars can be observed at intervals, yet it may be impossible to note the meridian passage of the same star at both places on the same night. Then the telegraph lines are usually the property of some commercial company and while their use for a short time might be freely granted, yet a protracted occupation of them as necessary when the meridians are distant from each other, would prove a serious hindrance to their regular business.

The method at this time most generally employed, is to observe at each station a number of stars entirely independently of the other. From these stars are deduced the clock errors and rates upon the respective local times. Then at some prearranged period, communication is opened between the stations, and a comparison of the clocks made which shows their exact difference at a given instant. By applying the error to the time as shown by the clock at this instant, the exact local time at each station is the result, and applying the difference between the clocks as shown by the comparison, the required difference of longitude is readily obtained.

These methods originated, as did the electric telegraph, in the United States, and soon after Morse's invention came into practical use, they were extensively employed by the Coast Survey, in accurately determining points in every part of the country that could be reached, no pains being spared to make the determinations as accurate as possible. Upon the completion of the first successful Atlantic cable in 1866, an expedition was organized and placed in charge of Dr. B. A. Gould, for the purpose of measuring the meridian distance between Greenwich and the Naval Observatory at Washington. This was successfully carried out in spite of numerous difficulties, and the result proved that the determinations already made upon which the most reliance was placed were decidedly in error. The result from the chronometric expedition in 1855 previously referred to differing over a second of time.

In constructing charts for use at sea, the accurate determination of latitude and longitude is of the utmost importance. The navigator starting on a voyage must know the exact position of his destination as well as the location of dangers to be avoided. He must know the error and rate of his chronometer when he sets out, but as the rate is not constant he should have some means of re-rating it at any place where he may stop. If the longitude of this place is well determined, the operation of obtaining the error and rate is an easy one, and may save his vessel from loss.

Surveys, of coasts or countries must have well established starting points, and while the latitude of a place is comparatively easy to determine, the longitude, except when the telegraphic method is used, is attended with more or less uncertainty.

In 1873, Commodore R. H. Wyman, U. S. N. Hydrographer to the Bureau of Navigation, organized by permission of the Navy Department, an expedition for the telegraphic determination of longitude in the West Indies and Central America. The submarine cables of the West India and Panama Telegraph Co. had just been completed, extending from Key West through Havana and Santiago de Cuba, south to Jamaica and Aspinwall, and east through the Virgin and Windward Islands to the northeast coast of South America, thus affording admirable facilities for the accurate determination of many points. It had long been known that the longitudes of various points in the West Indies and in Central and South America, did not harmonize, there having been no systematic attempt to determine them with relation to each other or to a common base. Longitudes in the western part of the Caribbean Sea depended upon the position of the Morro lighthouse at Havana, which had been determined by occultations. Further to the eastward, positions depended upon that of Fort Christian at St. Thomas. This in its turn depended upon the observatory of Major Lang in the Island of Santa Cruz about forty miles distant. This position depended upon numerous observations of moon culminations and occultations. Martinique and Guadeloupe in the Windward Islands had been surveyed by French officers who based their positions upon longitudes derived from moon culminations. The absolute determination of these starting points would of course fix all points derived from them.

The U. S. Steamer Fortune was designated by the Navy Department for the conveyance of the expedition, and Lieut. Commander (now Commander), F. M. Green, U. S. N. was placed in charge. This officer had given great attention to the subject, was a practiced observer, and exceptionally well qualified for the position. The services of Mr. Miles Rock, a skillful astronomer and computer who is now chief of the boundary survey of Guatemala, were obtained as principal astronomical assistant. The breaking out in the autumn of 1873, of the trouble with Spain and Cuba, over the Virginius affair, delayed the expedition until the next year, but in November 1874, a start was made from Washington, and after a short stay in Kingston, Jamaica, Aspinwall was reached early in December. Mr. Rock with one set of instruments proceeded immediately to Panama, while Lieut. Commander Green remained in Aspinwall with the other. The outfit for each party consisted of:—first, a portable observatory. This was made of wood in sections, framework of ash, covered with tongued and grooved pine boards. The sections were connected when set up by iron knees and bolts. When packed it was not difficult to transport, and it could be put up, or taken down in an hour. When set up it was about eight feet square, with doors in all sides, and a shed roof. The roof was made in three sections, the middle one being hinged so that it could be raised for observing. These observatories proved to be very strong and serviceable. They remained in use for a number of years with occasional slight repairs, were transported many thousand miles and set up in a great number of places in Europe, Asia, North and South America. They were designed by Mr. J. A. Rogers, and constructed at the Washington Navy Yard. Upon arriving at a point where observations were to be made, after obtaining the necessary permits from the local authorities, a suitable location for the observatory was the first consideration. The essential requirements were, a clear view of the heavens in the meridian, firm ground, a spot secluded enough not to attract attention from inquisitive idlers, and proximity to the telegraph office, or end of the telegraph line. Such a spot being found and permission being obtained from the owner for its use, an approximate meridian line was laid out by compass, and the house set up with reference to it. Experience soon showed the advisability of making certain additions to the observatory not contemplated by the designer, but which added much to convenience and comfort. A foundation was made, of timbers about six inches square, mortised together at the ends which could be placed in position and leveled before the observatory was set up, rendering this operation much easier and giving greater stability. A floor was laid upon joists supported by this foundation. Shelves were put up at various points, affording resting places for tools and small instruments, while a table in one corner, supported the chronometer, and offered a convenient place for an assistant to record observations, etc.

The principal instrument used was the transit. Those furnished for the use of the expedition were designed by Mr. J. A. Rogers, and constructed under his supervision in the repair shop of the Hydrographic office. The object glasses, made by the Clarks at Cambridge, were of 2½ inches clear aperture with a focal length of thirty inches. The instruments were of the prismatic or "broken" form in which the eye-piece is at one end of the axis, and the light is reflected from the object glass to the eye by a prism placed at the junction of the telescope tube with the axis. The observer does not have to change the position of his eye, no matter what the zenith distance of the star may be. This renders observation much less fatiguing and conduces to accuracy. The eye-piece was furnished with the usual spider line reticle and also with a filar micrometer for the measurement of zenith distances for latitude. A vertical finding circle was on the eye-piece end of the axis, and the instrument was provided also with a horizontal circle, fourteen inches in diameter, graduated to ten seconds. Other necessary parts were the striding and zenith telescope levels, and the illuminating lamps. The ends of the axis were supported by Ys at the ends of a transverse arm which in its centre was screwed to the top of a vertical axis supported in a socket surmounting the tripod. This vertical axis was slightly conical in shape and accurately fitted into its socket. A screw was so placed underneath, that the axis, and with it the instrument, could be raised slightly, when it was easily revolved horizontally into any desired position, a reverse movement of the screw then lowered the axis into its seat, when the instrument was held firmly by the friction. For supporting the instrument there was used at first, a portable pier made in the shape of the frustrum of a cone, of strong oak staves, firmly bound with iron hoops, and when set up, filled with sand or earth. Subsequently a brick pier was found to be more stable and the wooden ones were discarded.

Of equal importance with the transit was the Chronometer. The expedition was supplied with four of these made by Negus of New York. They were regulated to sidereal time, and provided with a break circuit arrangement. This consists of a toothed wheel acting on a jewel pallet attached to a light steel spring. In this spring is a platinum point, which touches another platinum point, except when the spring is acted upon by the toothed wheel. These points are connected respectively with terminals on the outside of the chronometer, and are insulated from each other except at their point of contact. The electric circuit is complete through the chronometer except when the teeth of the wheel acting on the jewel pallet separate the points. The circuit is opened for about one-fortieth of a second and closed during the rest of the time. One tooth in the wheel is omitted and the circuit remains unbroken at that point which is the beginning of each minute. Each chronometer is provided with a condenser to take up the extra current, and avoid burning the contact points. These chronometers were most excellent instruments, the rate was generally small and very regular, and did not seem to be influenced in any way by the passage of the current. They are still in use, and are as efficient as ever.

The expedition was at first provided with a substitute for the chronograph in the shape of the old fashioned Morse telegraph register. In this a steel point or stylet was pressed by the action of an electro-magnet against a long fillet of paper, unwound by clock-work at a rate more or less regular. This magnet was in circuit with the chronometer and with a break circuit key in the observer's hand. As long as the electric circuit was closed the stylet made a continuous indented straight line on the paper; but as soon as it was broken, either by the chronometer or the observer's key, the stylet flew back and left the paper unmarked until the circuit was again closed. The effect of the action of the chronometer was to graduate the fillet of paper into a series of straight indentations, from one to two inches in length, separated by unmarked spaces from ¹/16 to ¹/8 inch in length. When the key was pressed an independent clear space was left on the paper, and by the relation in distance between the beginning of this space and the beginning of the second spaces immediately preceding and following, the time of pressing the key was determined. The omission of the break at the sixtieth second, made the mark of double length, and hence the beginning of the minute was easily recognized. These instruments served their purpose very well, but had several disadvantages. The rate of movement of the paper was not regular; when the clock-work was first wound up the motion was rapid and the second spaces long, and as the spring ran down the marks became shorter and shorter. Another drawback was the great length of the fillet; with spaces only an inch in length, it required five feet of paper to record a minute in time, and after a night's observation, there would be several hundred feet to examine, measure and record, occupying the greater part of the following day. By stopping the instrument between the observations something was gained in this respect, but this tended somewhat to confusion and error in keeping the record. They were only used for one season's work, and in their stead were procured two cylinder chronographs, made by Bond of Boston. These were fine instruments, but somewhat too delicate to stand the necessary transportation. In these instruments as in most other chronographs, a cylinder about six inches in diameter is made to revolve by clock-work once in a minute. An electro-magnet mounted on a carriage actuated by the same clock-work moves alongside the cylinder, in a direction parallel with its axis, at the rate of about an eighth of an inch in a minute. The armature of the magnet carries attached to it a pen, the point of which rests upon a sheet of the paper wrapped around the cylinder. While the circuit through the coils of the magnet is complete, the pen makes a continuous spiral line upon the paper, but when the circuit is broken by the chronometer, or key, it flies to one side making an offset, and immediately returns to its position, as soon as the circuit is again closed. The result is to graduate the whole surface of the paper into second spaces, from which the observations can be read off with the greatest ease.

For supplying the electric current, there was used at first, a modification of the Smee battery, but this proving very uncertain in strength, a gravity battery was substituted, and afterwards a number of LeClanché cells were procured.

Upon the first expedition, no telegraph instruments were carried, but the use of such as were needed was easily obtained from the telegraph companies. The line between Aspinwall and Panama was in good condition and no trouble was experienced in exchanging the time signals by which was effected the comparison of the chronometers. Wires were stretched from the observatories in each place to the respective telegraph offices, and for the exchange of signals were connected directly to the ends of the line.

Everything being ready, the routine of the work was as follows:—The transit being carefully leveled was placed in the meridian by observation of zenith and circumpolar stars. From six to ten time stars, and two or three circumpolars were then observed, the instrument was reversed in the Ys and nearly the same number of stars observed in the new position. At some time agreed upon, generally when the regular work of the telegraph line was over for the day, the wires were connected up and one of the operators came to the observatory to assist in holding communication. By a simple arrangement of relays, in the line and chronograph circuits the chronometer at one station was made to register its second beats on the chronograph at the other, which was all the time being graduated into second spaces by its own chronometer. This was done for about five minutes and the times of beginning and ending noted. Then the connections were reversed and both chronometers allowed to beat for five minutes on the chronograph at the first station.

This method of exchanging signals was only practicable on land lines or very short cables. The ordinary relay used on a land line requires a strong current to work it, and would not be affected in the least by the delicate impulse sent over a long cable, consequently when the expedition came to compare chronometers over the 600 miles of cable between Aspinwall and Kingston, it was necessary to use another method. At that time the instrument in general use on submarine cable lines was what is known as Thompson's mirror galvanometer. It consists of a coil of very fine insulated wire wound with great care on a spool or bobbin of vulcanite, about three inches in diameter and 1½ inches thick. In a hole in the centre of the spool is made to slide a small tube, so that the end of the tube will be in the centre of the coil. In the end of the tube is mounted a small mirror, swung in a vertical position on a single upright fibre of silk. Horizontally across the back of this mirror is secured a small permanent magnet, in length about the diameter of the mirror or about one-eighth to one-quarter of an inch. The mirror and magnet together weigh only one or two grains. When an electric current is sent through this coil it deflects the magnet and with it the mirror to the right or left. The apparatus is exceedingly sensitive so that it is influenced by very feeble currents. Communication has been maintained with an instrument of this kind over the Atlantic cables, by the current proceeding from a battery composed of a single copper percussion cap with a small scrap of zinc and a drop of acidulated water. The use of the mirror is to make visible the movements of the magnet. The coil is mounted upon a standard so as to be about eight inches above the table. At the distance of eighteen inches or two feet is placed a lamp. This is surrounded by a screen which cuts off all the light, except that which passes through a tube directed towards the mirror. Lenses in the tube focus the light on the mirror and thence it is reflected to a vertical white surface, a sheet of paper for instance, at a suitable distance and appears as a small and brilliant spot. A movement of the magnet causes a horizontal deflection of this spot to the right or left depending upon the direction of the current passing through the coil. As these movements can be produced at will by means of the key at the sending station, it is only necessary to apply to them the dots and dashes of the Morse alphabet, to have a very ready and perfect means of communication. To the uninitiated spectator the facility with which the practiced operator translates these apparently meaningless movements is remarkable. If the cable is long and not in good condition the signals are sometimes almost imperceptible, while any slight jar of the table or apparatus will produce a large and irregular effect. Earth currents also will cause vibrations hard to distinguish from the signals, and if, as sometimes happens, the battery is connected in the wrong way, the signals will be reversed. In spite of these drawbacks the skillful operator reads off the message and rarely makes an error. This instrument is still in use on some of the cable lines, but on most of them it has been replaced by a recording instrument, also the invention of Sir Wm. Thompson, which is almost as sensitive, and of which I will speak later on. The key used in connection with these instruments, both the mirror and recorder, is arranged with two levers, so connected that pressing one of them causes a current to be sent over the line in one direction, while the other sends it in the opposite.

The method adopted for comparing chronometers by means of these instruments was as follows:—Everything being ready for the exchange of signals, the observer at one station seated himself, where he could see the face of the chronometer, with his hand on the cable key. At ten seconds before the beginning of a minute as shown by the second hand, he pressed his key several times in quick succession, thus sending a series of impulses through the line, which appeared at the other end as a rapid movement of the light to and fro. This was a warning signal, and the observer at the second station with his eye on the light, tapped his chronograph key in the same way making a series of marks, which indicated the beginning of the comparison. The first observer exactly at the sixtieth second by his chronometer pressed his key quickly and firmly and repeated this operation at every fifth second for one minute. The second observer tapped his key promptly as soon as he saw the light move, thus registering the time on his chronograph. The minute at which the first signal was sent, was then telegraphed, and repeated back, to insure against error, and the operation was repeated until sixty-five signals had been sent from one station and received at the other. Then the second observer sent the same number of signals to the first in precisely the same manner, thus giving sixty-five comparisons of the chronometers in each direction. The results derived from this method are affected by errors from two causes. One is the personal error of the observers in sending and receiving signals and the other the time consumed by the electric impulse in traveling over the line and through the instruments. If the same strength of battery is used at each station, and the resistance of the instruments is the same, the errors arising from this latter source will be eliminated by the double exchange. The observer sending the signals kept his eye on the chronometer and counted the second beats by both eye and ear, moving the hand which he had on the key slightly in unison with the beats, and could thus be sure of pressing the key at the proper time within a very small fraction of a second. At the other end of the line, considerable time is lost after the actual movement of the light before the observer can press his chronograph key, and the principal error affecting the result is the difference of this time in the two observers, which was found to be very small.

As I have said, the cable was first used in the measurement between Kingston and Aspinwall, Lieut. Commander Green occupying the former station, and Mr. Rock the latter. After the successful completion of this link, measurements were made from Santiago de Cuba to Kingston, and to Havana. It was the intention to measure from this last point to Key West, but about this time yellow fever broke out there and the expedition was ordered by the Secretary of the Navy to return. The Fortune arrived at Washington in April, 1875, and the time until November was spent in working up the winter's observations. Speaking in a general way this work is as follows:—From observations extending over many years, the exact positions in the heavens of a large number of fixed stars have been found, so that their times of passing any meridian can be computed with great accuracy. The transit instrument is furnished with an eye-piece containing a number of parallel lines usually made of spider silk. These are placed in the focus of the instrument, and it is set in position, so that the middle line of the group is in the plane of the meridian. The observer provides himself with a list of desirable stars, and setting his instrument on those he may choose, records the time at which they pass each of the spider lines, by tapping his chronograph key. If there were no instrumental errors to be discovered and allowed for, if the star's place were known absolutely, and the observer had no personal equation, then it would be only necessary in order to find the error of the clock, to observe one star upon the middle line of the reticle. The difference of the clock time of transit and the real time as already known, would be the clock error and no further trouble would be required. But as none of these conditions are fulfilled, it is necessary to multiply observations in order to eliminate accidental errors, and to obtain instrumental corrections which may be applied so as to get the most probable result. Accidental errors of eyesight and perception are nearly eliminated by taking the star's transit over several lines instead of one and using the mean. Some of the instrumental errors are from the following causes. If the pivots which support the telescope are unequal in size the axis of the tube will be thrown to one side or the other of the meridian, and the star will be observed either before or after it crosses. The weight of all transit instruments causes a flexure of the horizontal axis and this effect is at its maximum in those of the prismatic pattern. The spider lines must be adjusted so that the middle one is exactly in the axis of the tube, or as this can seldom be done the resulting error, called the collimation, must be found. The horizontal axis of the instrument must be as nearly level as possible, and the error in this respect must be found by frequent applications of a delicate spirit level. Finally the instrument must be directed as nearly as possible to the north and south points of the horizon, and a correction must be made for any error in this respect. The result of each of these errors is to cause the star's transit to be recorded too early or too late, and to get the true result they must all be found and applied with their proper signs. The inequality of pivots and the flexure correction are found by delicate measurement and observations, when the instrument is first used, and are recorded as constants to be applied in all subsequent work. The level tubes are graduated and the value of their divisions obtained in angular measure. The collimation error is found by observing stars near the zenith in one position of the instrument and then reversing and observing others, or by taking the transit of a slow moving star over a portion of the spider lines then reversing and observing the same intervals in the opposite order. The error of azimuth, or deviation from the north and south line, is found by comparing the observations of stars whose zenith distances differ considerably. These corrections all being found and applied to the observation of each star, the result is the correct time of transit as shown by the chronometer, and the difference between that time and the true time, is the error of the chronometer. A mean of the observations of several stars on the same night, gives a very accurate value for this clock error, and by comparing the results of several nights' work, the rate is found. By applying the rate to the clock error it is reduced to any required epoch, as for instance, the mean time of the exchange of time signals, and the difference of longitude is easily found. As may be imagined the computation and application of all these errors, exercising the greatest care to insure accuracy is a long and tedious process. The operations described give a very close result, but in order to arrive at the greatest accuracy obtainable the computations are made again by the method of least squares.

In the Autumn of 1875, the expedition again took the field, this time in the side wheel steamer Gettysburg, which was much better adapted to the work than the Fortune. The first link measured was between Key West and Havana. Key West had already been telegraphically determined by the Coast Survey, and now afforded a base for the system of measurements completed and for those to follow. The next measurement was between Kingston and St. Thomas. Then from the latter place to Antigua and to Port Spain, Trinidad. From Port Spain, measurements were made to Barbadoes and Martinique. The position at St. Thomas was then re-occupied, and measurements made thence to San Juan, Porto Rico, and to Santa Cruz. This ended the work in the West Indies, differences of longitude having been measured between nearly all the important points connected by telegraph. The Latitude of all the stations, was also determined by the zenith telescope method, and the position of the stations was referred either to the observation spot previously used, when that could be identified, or to some prominent landmark.

Between St. Thomas and Santa Cruz, the measurement was made twice, the observers exchanging stations at the completion of the first series of observations. This was to eliminate the effect of their personal errors, and to obtain a value of these, which might be applied to the other measurements. It has long been known that different people perceive the same phenomenon at different times, varying with different individuals, but reasonably constant with the same individual. In the particular case of observing the transit of a star, most people will record it on a chronograph from one to three tenths of a second after it happens. In the method of observing by eye and ear the error is generally much greater. The whole question of personal equation, however, is a mixed one and I will not attempt to discuss it, but will only give some of the results obtained in this particular work. In longitude measurements the error from this cause is half the difference of the personal equation of the two observers. If this difference remained constant, then it would be easy to find it once for all, and apply it to all measurements made by the same observers. In the West India work, it was assumed that it did remain constant, and half the difference between the two measurements made from St. Thomas to Santa Cruz, was applied to all the other links. The correction was quite small, being only 0^s.025. In subsequent work by the same and other observers it was deemed wiser not to apply any corrections at all, rather than one that was probably not exact, and might be much in error. To show the fluctuations to which this elusive quantity is subject, I will cite the results of some observations made to determine it, by observers engaged in this same work at a subsequent period. In April and May, 1883, at Galveston, Texas, two observers D. and N. having just completed a telegraphic measurement between that place and Vera Cruz, Mexico, made some observations for the determination of their relative personal equation, by observing transits of alternate stars under the same conditions as near as possible. Both used the same instruments, transit, chronometer and chronograph. On April 30, two sets of observations were made, showing the difference of the equations to be 0^s.26. On May 1, one set gave 0^s.32, and another 0^s.29. On May 2, only one set was made giving 0^s.36, a variation of 0^s.07 in two days. In June 1884, one year later, another series of observations of the same character was made at the Naval Observatory in Washington, and on the same nights the personal equation machine invented by Prof. Eastman, was used as a comparison. This is an instrument in which an artificial star is made to record its own transit over the wires of a reticle, while the observer records the same with a chronograph key. The difference is manifestly the personal error of the observer. This gives the absolute equation of the observers, and their difference is the relative equation, and should accord with that found by the method of alternate stars. Some of the results were as follows:—On June 4, the difference by machine of their personal errors was 0^s.16 and by star observations 0^s.24, on the 15th of June the machine gave 0^s.10 and the stars 0^s.24, on the 16th, machine 0^s.14, stars, 0^s.13, a very close agreement, on the 17th, machine gave 0^s.07 and stars 0^s.18. The observer N. combined with another, C., who had not had as much experience in observing, gave still more discordant results. On June 20, the machine gave as their relative equation, 0^s.08, while star observations gave 0^s.27, on June 23, machine 0^s.13, stars 0^s.51, and on June 28, machine, 0^s.20, stars 0^s.35. In the case of the first two observers a mean of the determinations amounting to about 0^s.20 might have been applied to the measurements made by them, but as these were made under all conditions of climate, in latitudes varying from 30° N. to 36° S. and in different states of health and bodily comfort, it was concluded not to introduce any correction at all rather than one that might be considerably in error. In all of the work it has been the custom as far as possible to place the observers alternately east and west of each other, so that the result of personal error in one measurement is neutralized to a greater or less extent in the next. Of course the method of exchanging stations and making two measurements of each meridian distance would afford the best solution of this problem, but except in certain favorable conditions, this is precluded by considerations of time and expense. In the measurement between Galveston and Vera Cruz mentioned above, it had been the intention to exchange stations, but by the time the first measurement was finished the season was rather far advanced, there was danger of yellow fever in Vera Cruz and an observer going there at that time, if he escaped disease would have had the certainty of being quarantined from entering the United States for three weeks or a month after leaving Mexico.

Upon the completion of the West Indian work, and the publication in 1877, of the results, it was determined by the Bureau of Navigation to send an Expedition for the same purpose to the east coast of South America. Cables were in use extending from Para in northern Brazil to Buenos Ayres in the Argentine Republic. A cable had at one time connected this system with the West Indies, through British Guiana and Trinidad, but one of the links was broken and there was no prospect of its repair, otherwise the Station established at Trinidad in 1874 might have been taken as the starting point. There was direct communication however between England and Brazil, by the way of Portugal, and the Madeira and Cape de Verde Islands. Lisbon seemed to afford the most convenient place to start from, but its longitude had never been determined by telegraph and it was decided to request the French Bureau of Longitudes to coöperate by making this measurement from Paris. This request was readily granted, but for some reason the agreement was not kept. For the use of the Expedition the old fashioned sailing ship Guard was furnished and Lieut. Com. Green was given command. Mr. Rock being otherwise employed his place was taken by Lieut. Com.(now Commander) C. H. Davis, U. S. N. The instruments having been placed in good order, and new supplies furnished where necessary, the expedition sailed from New York for Lisbon in the latter part of October, 1877. The Guard was a slow sailer, the weather was rough and the wind generally ahead, consequently a month was consumed in making the passage. It was the intention to make the first measurement between Lisbon and Funchal, Madeira. Lieut. Com. Davis with party and instruments occupied the latter station, proceeding by mail steamer at the first opportunity. The cable from England does not land directly at Lisbon, but at a small town called Carcavellos on the coast about twelve miles from the city. As it was not practicable to connect the land line from Lisbon direct to the cable, it was necessary in making the exchange of signals to adopt another method, or rather combination of methods. An officer of the ship was sent to Carcavellos, furnished with a chronometer and chronograph. When the time came for exchanging signals, he first compared his chronometer with that at Lisbon, by the automatic method, in use on land lines, then with the Funchal chronometer over the cable using the mirror galvanometer. Finally a second automatic comparison was made with Lisbon. From the data furnished by these comparisons it was an easy matter to compute the difference between the chronometers at Lisbon and Funchal. The Lisbon party had been received with great courtesy by the director of the Royal Observatory, Capt. Oom of the Portuguese Navy, and had been given the use of a small detached observatory near the main building. The party at Funchal selected a site on the ramparts of an old fort, which afforded a clear view and was near the landing place of the cable. Here occurred an accident to the transit instrument, which fortunately was easily remedied. Near the beginning of the observations on the first night the wind, which was blowing almost a gale, lifted a part of the roof off the observatory, and dropped one section of it inside. The transit was knocked off the pier, and was at first thought to be much injured. Fortunately the precaution had been taken to bring along a couple of spare instruments, borrowed from the Transit of Venus Commission for use in case of such an accident. The Funchal party was provided with one of these, which was set up for use by the next night, and the injured one was sent to Lisbon for repairs. The injury proved to be less than supposed and the repairing was an easy matter. Upon the completion of this measurement the Lisbon party proceeded to St. Vincent one of the Cape de Verde Islands. This is a barren and desolate spot of volcanic formation, but being on the route of steamers from Europe to Africa and South America is of much importance as a coaling station. Measurements were made from this point to Funchal and to Pernambuco in Brazil, and the Guard then sailed for Rio Janeiro. Upon arriving at that point after a long passage, it was found that the cable between Rio and Pernambuco was broken, and there being no immediate prospect of its being repaired, the Pernambuco party was ordered by mail steamer to Rio, and thence to Montevideo. A measurement was made between Rio and Montevideo and then between the latter place and Buenos Ayres, Lieut. Com. Green occupying the Montevideo station for that purpose. The position of the observatory at Buenos Ayres was referred to that occupied by Dr. B. A. Gould, Director of the Argentine National Observatory, in a similar measurement a short time before between that place and Cordova.

Both parties now returned to Rio, only to find that the cable was still broken. In order to be ready for work as soon as it should be repaired, Lieut. Com. Green proceeded to Bahia with the ship and established a station there, Lieut. Com. Davis with his party remaining in Rio. After waiting a month, and there still seeming to be no prospect of the repair of the cable, the expedition finally sailed for home, arriving at Norfolk, Va., after a pleasant and uneventful voyage of forty-five days. Repairs to the cable were not completed until several months afterward. In May of the next year, the party was again sent out, to complete the measurement on the Brazilian Coast, and also to measure from Greenwich to Lisbon, the French Bureau of Longitudes having failed to carry out its promise to measure from Paris. There being no ship available for the purpose the traveling was done by mail steamer. Upon arrival in England, an interview was had with the Astronomer Royal, who readily agreed to assist in the work. Lieut. Com. Green accordingly established his observatory at the landing place of the cable at Porthcurnow in Cornwall, and Lieut. Com. Davis proceeded to Lisbon and occupied the station used there the year before. Owing to the foggy and rainy weather prevalent in England at that season, it was found impossible to make any astronomical observations at the Porthcurnow observatory. The work was therefore done in this way:—Observations were made at Greenwich and at Lisbon, and Porthcurnow and Carcavellos were used as transmitting stations. The chronometer at Porthcurnow was compared automatically with the clock at Greenwich, and by cable with the chronometer at Carcavellos. The latter was compared automatically with that at Lisbon, before and after the cable exchange. At this time there were made at Carcavellos, some experiments with a view to making the receipt of the time signals over the cable automatic, thus doing away with the personal equation of the receiver. The instrument in use for the regular business of the cable was what is known as the siphon recorder, also the invention of Sir Wm. Thompson. In this a small coil of fine wire is suspended by a fibre of silk, between the poles of a powerful permanent magnet. The currents from the cable pass through this coil and the action is to deflect it to the right or left, just as the mirror is deflected in the instrument already described. Attached to this coil is a siphon made of a capillary glass tube. One end of the siphon dips into a reservoir of aniline ink, and the other hangs immediately over the centre of a fillet of paper, which is unwound by clock-work. If the siphon touched the paper, the feeble currents sent through the cable would be powerless to move it, on account of the friction, and in order to produce a mark some means must be found of forcing the ink through the capillary tube. This is accomplished by electrifying the ink positively and the paper negatively, by means of a small inductive machine, driven by an electric motor. The effort of the two electricities to unite, forces the ink through the tube and it appears on the paper as a succession of small dots. When the paper is in motion and the coil at rest, a straight line is formed along the middle of the fillet by these dots, but as soon as a current is sent through the coil the siphon moves to the right or left making an offset to this line. These offsets on one side or the other are used as the dots and dashes of the Morse alphabet. A time signal sent over the cable while this instrument was in circuit, appeared as a single offset on the paper, and it was only necessary to graduate the paper into seconds spaces by the local chronometer, in order to have the automatic record required. The ordinary chronometer circuit could not be put through the coil directly, as it would then charge the cable and interfere with the signals, and besides, the current, unless by the introduction of a high resistance it was reduced in strength, would infallibly give such a violent motion to the coil as to break the siphon, if it did no other damage. The result was obtained in this way; an ordinary telegraph relay was put in the chronometer circuit and the armature of course moved with the beats. To this armature was fastened one end of a fine thread. The other end was attached to a slender piece of elastic brass which was fixed at one end to the framework supporting the paper, in such a way that the other end touched the metallic vessel holding the ink, except when the thread was drawn tight enough to pull it away. This the armature of the relay did while the circuit through the chronometer was complete, but as soon as it was broken at the beginning of a second, the tension of the thread was relaxed and the brass sprung back against the ink well, allowing the positive and negative electricities to unite independently of the siphon. The ink then ceased to flow, until the spring was drawn away, thus leaving a small blank space in the line of dots and forming a very good chronographic record. This was liable to a small error due to the length of time that elapsed between the release of the spring by the armature and its impact on the ink well. Had there been time for more extensive experiment this difficulty might have been overcome. Or if the same method had been adopted at both stations, the result would have been affected by only the difference between the times of movement of the brass spring which would have been minute. Lack of time for experiment, and the fact that the observers were averse to introducing untested methods into a chain of measurements most of the links of which were already completed, prevented any use being made of this achievement. The measurement between Greenwich and Lisbon being satisfactorily completed, Lieut. Com. Green by order of the Navy Department returned to the United States, and the links between Rio and Pernambuco and between the latter place and Para, were measured by Lieut. Com. Davis and the writer, completing the work of the expedition, after which the party returned to Washington.

The computation of this work, showed the somewhat surprising fact that the heretofore accepted position in longitude of Lisbon, differed from the true one by about two miles. The longitude of Rio Janeiro had always been more or less in doubt, various determinations had differed by as much as nine miles, but the position finally decided upon by the best authorities agreed very closely with that obtained by telegraph.

The next expedition was sent out by the Bureau of Navigation to China, Japan and the East Indies, Lieut. Com. Green being still in charge. The officers composing the party sailed from San Francisco by mail steamer in April, 1881, for Yokohama, where they joined the U. S. Steamer Palos. From Hong Kong north to Vladivostok in Eastern Siberia the cables were owned by a Danish company. From Hong Kong to the south and west they were the property of English companies. Beginning at Vladivostok observations were made at all stations on the Asiatic coast except Penang, as far as Madras, India. It was intended to try and make some use of the automatic method of receiving time signals, on this work, but on arriving in Japan it was found that the recording instrument used by the Danish company was entirely different from that used by the English lines. It consisted of a series of electro-magnets acting on a single armature, which carried a siphon made of silver. The signals consisted of long and short movements, to one side of the middle line, instead of equal deflections on both sides as in the Thompson recorder. An attempt was made to convert this instrument into a relay, by causing the siphon to make and break a circuit, but it was not successful. The movements of the siphon were not regular enough, and the contact was not firm. Consequently the mirror method of exchanging signals was still adhered to.

The longitude of the position occupied in Vladivostok, had been determined telegraphically from Pulkova, by the Russians, using the land lines across Siberia. The English had also determined the position at Madras, using the cables through the Mediterranean and Red Seas. The work of the United States Expedition joined these two positions, completing a chain of measurements extending over many thousand miles, made by observers of different nationalities in various climates. It was to be expected that considerable discrepancy would be found in the final result, but taking the longitude of Vladivostok as brought from Madras, and comparing it with that determined by the Russians, the difference was only 0^s.39. Taking everything into consideration, this result was gratifyingly close. Upon the conclusion of this series of determinations, the connection of Lieut. Commander Green with the work was severed, he receiving his promotion to the rank of Commander.

The next work was under the charge of Lieut. Com. Davis, and consisted in the determination in 1883-84, of positions in Mexico, Central America and the west coast of South America. Cables had just been completed, extending from Galveston, Texas, to Vera Cruz, thence across Mexico to the Pacific and down that coast to Lima, Peru, where connection was made with another system extending to Valparaiso. Galveston was a point determined by the Coast Survey, and the measurement thence to Vera Cruz was the first one made. It was completed in May '83, and in the Autumn of the same year the party proceeded to the South American coast, and stations were established and observations made at various points from Valparaiso to Panama, and at one point, La Libertad, in Central America. It was at first the intention to extend the series across the Isthmus of Tehuantepec and connect with Vera Cruz, but lack of time prevented this, and as the station at Panama determined nearly ten years before, afforded a convenient starting point, the idea was abandoned. From Valparaiso, a measurement was made with the coöperation of Dr. Gould to his observatory at Cordova, using the line across the Andes, and exchanging signals automatically. These measurements constituted the final links in a long chain, extending from the prime meridian Greenwich across the Atlantic to the United States, thence via the West Indies to Panama, down the west coast of South America to Valparaiso, across the Andes to Cordova and Buenos Ayres, up the east coast to Pernambuco, across the Atlantic to Lisbon, and thence to Greenwich, altogether a distance of eighteen to twenty thousand miles. The two longitudes of Cordova, as brought from Greenwich by the two routes, differed from each other by only 0^s.048, a result which speaks well for the accuracy of the methods employed. When preparations were being made for this expedition, it was determined to accomplish if possible something in the way of getting rid of the personal equation in exchanging signals. An idea which had been suggested by work done by Major Campbell, R. E. in the measurement between Bombay and Aden, seemed to promise well. It was to be used with the siphon or other form of recorder. The ordinary double current cable key with two levers, was arranged with an additional lever in such a manner that while in ordinary use in the telegraph office, it could also be put in circuit with the chronometer and chronograph in the observatory, and a signal sent through the cable would have its time of sending registered on the chronograph. Ordinarily in speaking over a cable line, connection is made in such a way that the current sent does not pass through the recorder at the sending station, as a violent movement of the siphon would result. By means of a shunt, however, it is possible to control this movement somewhat. Suppose now, that the connections at each station are made in such a way, by means of this key and the shunt, that a signal sent from one, is registered on both recorders and on the sender's chronograph. The observers leaving their assistants to take care of the chronographs, go to the respective telegraph offices, and all being ready, the observer A taps his key. This sends an impulse through the cable, which appears on A's recorder, as a violent jump or kick of the siphon. On B's recorder it is registered as a deflection like the ordinary dot or dash, at the same instant is recorded on A's chronograph the time of sending. As soon as B sees the signal on his recorder, he taps his key also registering the signals on both recorders and on his chronograph. A, seeing B's signal again taps his key, and so on, as long as desired. The result is that each observer has a record on his siphon fillet of all signals sent and received, while the times of those he sent are recorded on his chronograph. By the use of the diagonal scale and the Rule of Three, he can without difficulty find the times of the signals received. The siphon recorders are well made, and the paper moves with great regularity. This system was used in the measurement between Galveston and Vera Cruz with great success. It was intended to employ the same method throughout the measurement on the west coast of America, but on arriving at Lima, it was found that the company owning the lines south of that point still used the mirror galvanometer, and it was of course necessary to return to the old method. The improved key was used however, which eliminated the error in sending signals.

After this work was completed and the results published in 1885, nothing was done in this line by the Bureau of Navigation for some years. Upon the return of the writer in the spring of 1888, from a cruise in the South Pacific, he found that the subject of sending an expedition to complete the measurements in Mexico and Central America was under consideration in the Bureau of Navigation and the Hydrographic office. It was finally decided that the work should be done, and the writer was placed in charge. The instruments were brought out of their retirement, and by the aid of the Hydrographic Office a very complete outfit was furnished, and in November of last year a start was made from New York, the expedition proceeding by mail steamer to Vera Cruz. Here the spot occupied by Lieut. Com. Davis in '83 was found, his transit pier, which was still standing was repaired, and instruments mounted. Lieut. Charles Laird, U. S. N., who had been identified with the longitude work since the China expedition in 1881, was left in charge of the observatory at Vera Cruz, and the writer proceeded with his party to the small town of Coatzacoalcos, at the mouth of the river of the same name. This point is about one hundred and twenty miles southeast of Vera Cruz, and is the landing place of the cable. A land line extends from this point to Salina Cruz on the Pacific coast, a distance of about two hundred miles. In exchanging time signals between Vera Cruz and Coatzacoalcos, the automatic method was employed, the cable being short. The old wooden observatories were used at these points, but as they were too heavy for transportation across the Isthmus, tents made especially for astronomical purposes were substituted for them in the observations made on the Pacific coast. The journey across the Isthmus was slow, about two weeks being employed in traveling two hundred miles, though as the route was devious, the actual distance was nearer three hundred. Some of the instruments were heavy, and after being taken in canoes a hundred miles up the Coatzacoalcos river, against a rapid current, they were loaded on a train of pack mules, and carried the rest of the way by land. While the first party was crossing the Isthmus, the other was on its way from Vera Cruz, and being ready at about the same time, a successful measurement was made between Coatzacoalcos and Salina Cruz, exchanging signals automatically. The Coatzacoalcos party then crossed to Salina Cruz, while the other proceeded to La Libertad in Salvador, where the station established in the Spring of '84, was again occupied. The measurement between these places being completed, the Libertad party went on to San Juan del Sur, in Nicaragua, near the terminus of the proposed interoceanic canal. In the measurement between this point and Salina Cruz, as well as in the one preceding, the exchange was effected by mirror signals. This completed the season's work, and the two parties made the best of their way home via Panama, arriving in Washington in April and May respectively. The computation of the observations is not yet complete though well advanced; it was the intention to publish preliminary results this Fall, but owing to lack of time that can not be done.

Another piece of work is laid out for the same party for the coming winter, which is the measurement from Santiago de Cuba, through Hayti and San Domingo to La Guayra in Venezuela, over the cables of a French company, which have just been completed. This work will consume about six months, and the expedition which is to start almost immediately will probably return in April or May next. The determination of the longitude of La Guayra will give a point from which many other measurements may be made along the north coast of South America, furnishing material for extensive corrections of the charts of that region.

Having presented an outline of the work done so far, as well as that proposed for the near future, I will now mention some of the trials and tribulations, as well as the pleasures experienced in carrying out the object desired in an expedition of this kind. The greatest politeness and kindness have always been experienced from the officials and employees of the various telegraph companies over whose lines work has been carried on. The government officials of the foreign countries visited, have also invariably shown the utmost politeness, but sometimes this politeness has been visibly tinged with suspicion. The measurements in Peru and Chili were made amid the closing scenes of the war between the countries. Upon the arrival of the expedition in Lima, an interview was had with the Chilian Commander-in-Chief who had possession of the city, and permission was requested and readily granted to occupy a station in Arica. Upon arriving at the latter place some days after, the Chilian governor in charge was found to have instructions to facilitate the work, and readily granted permission to establish the observatory in a convenient locality, but flatly refused to allow a wire to be extended to the telegraph office, and also refused to forward to his immediate superior, a request that it might be allowed. He evidently supposed the party were emissaries of the United States, sent to treat secretly with conquered Peru, but how he expected this was to be done remains a secret. By a vigorous use of the telegraph in communicating with the U. S. Ministers to both Chili and Peru, his objections were silenced, and the wire was put up. The observatory at Arica was erected on the side of a hill to the windward of the town, because it afforded a clear view, and was less dirty than other eligible sites. It also was a safe position in case of a possible earthquake or tidal wave, by which Arica had already been twice visited with disastrous effect. In digging for a foundation for the transit pier, several mummies of the ancient Peruvians were unearthed at a depth of a foot. They had evidently belonged to the poorer class of people, as their wrappings were composed of coarse mats, instead of the fine cloth with which the wealthier people were usually interred. One was the body of a female with long hair, which had been turned to a reddish yellow color by the alkali in the soil. The whole coast of Peru is barren and desolate, except in the river valleys, it being seldom visited by rain, while it is nearly always overhung with heavy clouds and fog banks, which render astronomical work exceedingly difficult. Even when partially clear in the day time, it generally becomes cloudy at night. Many times the observer would be at his place before sunset ready to seize the first suitable star revealed by the darkness, only to be baffled by thick banks of cloud which would cover the entire sky in from five to ten minutes.

In northern Peru, with a latitude of about five degrees south, is the town of Paita. It is an assemblage of mud-colored houses, at the foot of high, mud colored bluffs. On top of these bluffs is a perfectly barren table land extending inland and up and down the coast for many miles. Before visiting it the observers were informed that its one good point was the perfect astronomical weather which always prevailed. Clouds were unknown, and such a thing as rain had never been heard of. The extreme dryness of the atmosphere was so favorable to health that no one ever died, and when a consumptive invalid was imported by the inhabitants in the hope of starting a cemetery, he blasted their expectations by recovering. Judge then of their feeling, when upon arriving at this delightful place, they were met with the information that while it was true that the sky was, in general, perfectly clear both by night and day, yet about once in seven years, rain could be expected, and that the year then present was the rainy one. And sure enough it did rain. The usually dusty streets became rivers and quagmires, the rocky valleys in the vicinity were transformed into roaring torrents, and the table land usually an arid desert became a swamp with a rank growth of vegetation. However by using every opportunity and snatching stars between clouds and showers the work was finally completed.

Upon arriving in Panama shortly after this experience, the party was met with the pleasant intelligence that yellow fever was prevalent, and that the foreigners were dying like sheep. Nearly every day of the party's stay, some one died of sufficient importance to have the church bells tolled for his funeral, while of the ordinary people little notice was taken. Every morning, the writer remembers passing a carpenter's shop where nothing was made but coffins, and the supply was evidently not equal to the demand, for finally the proprietor began to import them, apparently by the ship load. The weather however was delightful, and the nights were the most perfect, astronomically speaking, that could be desired.

The observers who went from Japan to Vladivostok were obliged to wait several weeks at Nagasaki, before an opportunity offered for proceeding to their destination, and when they finally arrived, the getting away again was a problem. Communication with the outside world by water was only open during the summer months, and even then it was more accidental than otherwise. The party established the observatory however, and settled down to work, letting the future take care of itself. In the early part of the work, rather an amusing incident occurred. As the community was full of all sorts and conditions of men, Koreans, Chinamen and Russian exiles, the last not political but criminal offenders; it was thought wise to have a sentry stationed at the observatory to guard against any possible harm to the instruments. So the Governor of the town was asked to furnish a soldier for that purpose, which request was readily granted, and one night the sentry was posted with orders to let no one touch the observatory. These orders he construed literally, and when the observers appeared to commence their night's work, he kept them off at the point of the bayonet. His only language being Russian with which the observers were not familiar, it was impossible to explain the true state of affairs, and it was only after hunting up an interpreter and communicating with his commanding officer that an entry was finally effected. A good deal of bad weather was experienced at this place, but at the end of six weeks enough observations had been made for the required purpose, and the party was fortunate enough to secure passage to Nagasaki, in a small steamer that had brought a load of coal out from Germany.

In the expedition to the Asiatic coast one of the most interesting experiences was the trip to Manila in the Philippine Islands. This is quite a large town when intact, but a great portion of it is usually in the condition of being shaken down by an earthquake or blown over by a typhoon. The inhabitants are full of energy, however, and find time between downfalls to build up again. The cable from Hong Kong lands at a point about one hundred and twenty miles from Manila, and the writer was directed to proceed thither, with a chronometer and chronograph for the purpose of transmitting time signals. The first part of the journey was made in a small coasting steamer uncommonly dirty, and occupied about thirty-six hours. At the end of that time the village of Sual in the Gulf of Lingayen was reached. This was distant from the cable station about thirty miles, and the remainder of the journey was made in a native boat, with mat sails, and bamboo outriggers, part of the time through channels between numerous small islands and for some distance in the open sea. The progress was slow, but it was a pleasant way of traveling, except for the sleeping accommodations which were primitive; consisting of a palm leaf mat thrown over a platform made of split bamboo, in which all the knots had been carefully preserved. About three days, including stoppages, were consumed in this thirty mile voyage, and the traveler finally reached his destination to be received with the greatest hospitality by the staff at the telegraph station, and just in time to allay the fears of the observers at Hong Kong and Manila who had begun to think him lost. About three weeks were spent here, and as the work only occupied a short time at night, the days were pleasantly passed in exploring the surrounding country, making friends with the natives, shooting and photographing the scenery. The return to Manila was by the same route and occupied nearly the same length of time.

The measurement from Singapore to Madras was over one of the longest lines of cable ever used for this purpose, the distance being about 1600 nautical miles. The Atlantic cables used by Dr. Gould in 1866 were a little more than 1,850 miles in length. There was an intermediate station at Penang about 400 miles from Singapore, where all the work of the line was repeated. For the longitude measurement however the cables were connected through to form an unbroken line. The mirror was the only instrument that could be used and even with this the signals were feeble and much affected by earth currents.

The observing parties have never been troubled by wild beasts, but while at Saigon in Cochin, China, a rifle was always kept handy for use in case of the appearance of a tiger. The observatory here was located near the edge of a jungle, and alongside the telegraph station, on the veranda of which a large tiger had been shot by one of the operators only a short time before.

In the expedition of last winter to Mexico and Central America, the principal annoyance was caused by insects which were numerous and malignant. At Coatzacoalcos they were found in the greatest abundance, though the whole isthmus of Tehuantepec is alive with them. Fleas and mosquitoes were expected of course, but added to this were numerous others much worse. Of the family of "ticks" four varieties were seen and felt, ranging in size from almost microscopic to a length of a third of an inch. The most numerous were about as large as a grain of mustard seed, and one who walked or rode through the bushes or high grass would find himself literally covered. One of the worst insects encountered was the "nigua" which is in appearance something like a small flea. It burrows into the toes and soles of the feet, lays a number of eggs, which hatch and produce painful sores. A gruesome story is current in that region, about an enthusiastic English naturalist, who found specimens of these encamped in his feet, and concluded to take them home in that way, in order to observe the effect, but died of them before reaching England. All the party were afflicted with these pests, but were always fortunate enough to discover them and dig them out with the point of a knife before any bad results were experienced. The village of Coatzacoalcos is prettily situated, the climate, especially in winter, is very agreeable and the river offers a commodious harbor, but as long as the insects are so unpleasant, few people will care to live there if they can avoid it.

There have been directly determined by these various expeditions, about forty secondary meridians. Many more positions depend upon these, so they may be said to have made a large addition to our accurate knowledge of the earth's surface. Telegraphic facilities are being constantly extended, and as the Bureau of Navigation has now a very complete outfit for this work, which only needs occasional repairs, it is hoped that it may be kept up for some time in the future.