OTHER COUNTRIES.
The beet sugar factory in Japan is said to be working with considerable success.
This year in Europe over 3,000,000 acres are devoted to beet cultivation. If the yield averages 12 tons, the crop of roots to be worked during campaign 1891-92 will certainly not be less than 36,000,000 tons, with a total yield of first grade sugar of about 7,300,000,000 lb.
Sugar sells for 9 cents per pound in Persia, where Russia has almost a monopoly of that business.
Finland imported, during 1889, 9,416 tons sugar, valued at $1,000,000. Germany supplied two-thirds of this at cheaper rates than Russia, owing to facilities of transportation. Two refineries are working; one of these uses exclusively cane sugar, while the other employs both cane and beet sugar.
A beet sugar factory in England, that has been idle for many years, is to resume operations under a new company, adopting the plan of growing a sufficient quantity of beets for an average campaign, independently of what all the farmers of the locality propose to do.
Siberia is to have a beet sugar factory. Experiments in beet cultivation have shown excellent beets may be raised there. Special advantages are offered by the Russian government, and factories are to be exempt from taxation daring a period of ten years. Sugar in Siberia is now considered an article of luxury, owing to distance and difficulties of transportation from manufacturing centers.
A special delegation from Canada has been sent to Europe, to study and subsequently report upon the true condition of the beet sugar industry.
A correspondent writes from Farnham, Canada, that the Canadian government grants a bounty of 2 cents per pound on beet sugar during campaign 1891-92. Duties on raw sugar were abolished last June.
AMERICAN WORKSHOPS.
An interesting paper on some of the leading American workshops was lately read before the members of the Manchester Association of Engineers on Saturday by Mr. Hans Renold. After expressing his opinion that the English people did not sufficiently look about them or try to understand what other nations were doing, Mr. Renold stated that he had visited that portion of America known as New England, and the works he had inspected were among the best in the United States. Among the many special features he had noticed he mentioned that in a Boston establishment where milling machine cutters were made he had found that £1 spent in wages produced as much as £30 to £40 worth of goods, the cutters being made at the rate of about sixty-four per hour by about a dozen men. Another noticeable feature was the exceptional care taken in storing tools in American workshops. These, in fact, were treated as if they were worth their weight in gold; they were stored in safes much in the same manner as we in England stored our money. He was, however, impressed by the fact that the mere understanding of the method of American working would not enable them to do likewise in England, because the American workmen had gone through a special training, and a similar training would be necessary to enable English workmen to adapt themselves to American machines. One very noticeable feature in American engineering shops which he visited was that all the machine men and turners were seated on blocks or stools at their machines, and the question naturally arose in his mind what would English engineers say if such a practice were adopted in their shops. In other ways he was also struck by the special attention devoted to the comfort of the workmen, and he was much impressed by the healthy condition of the emery polishing shops as compared with similar shops in this country. In England these shops in most cases were simply deathtraps to the workmen, and he urged that the superior method of ventilation carried out in the States should be adopted in this country by introducing a fan to each wheel to take away the particles, etc., which were so injurious. One very special feature in the United States was that works were devoted to the manufacture of one particular article to an almost inconceivable extent, and that heavy machine tools complete and ready to be dispatched were kept in stock in large numbers. American enterprise was not hampered as it too frequently was in England by want of capital; while in England we were ready to put our savings in South American railways or fictitious gold mines, but very chary about investing capital which would assist an engineer in bringing out an honest improvement, in America, on the other hand, it was a common practice among the best firms to invest their savings over and over again in their works, which were thus kept in a high state of perfection.
The above paper came in for some pretty severe criticism. Mr. John Craven remarked that although Mr. Renold had gone over a wide field of subjects, he had practically confined his remarks to Messrs. Brown & Sharpe's establishment, and while he (Mr. Craven) was ready to admit that so far as high class work and sanitary arrangements were concerned, Messrs. Brown & Sharpe's were a model, they could not be put forward as representative of American establishments generally. As a matter of fact, many of the American workshops were not as good as a large number of similar workshops in Manchester. Mr. Renold had referred to the extensive use of gear cutters in the United States, but he might point out that it was in Manchester that the milling machine was first made. Mr. Samuel Dixon said he had certainly come to the conclusion that no better work was done in America than could be and was being done in this country; while as regards the enormous production of milling cutters, that was simply an example of what could be done where large firms devoted themselves to the production of one specialty. With regard to the statement made by Mr. Renold that the American thread was preferable to the Whitworth thread, he might say he entirely disagreed with such a conclusion, and he might add that after visiting a variety of Continental and American workshops he should certainly not, if he were called upon to award the palm of superiority in workmanship, go across the Atlantic for that purpose. Mr. J. Nasmith remarked that whether English engineers were the inventors of the milling machine or not, it must be admitted that it was through this type of cutter being taken up by the Americans that milling had become the success it was at the present time. English engineers were very conservative, and it was only through the pressure of circumstances that milling machines came into general use in this country. When American inventions were brought to England they were generally improved to the highest degree, but he thought the chief fault of both American and Continental engineers was what one might call "over-refinement;" there was such a thing as over-finishing an object and overdoing it. If, however, American machinery was so much superior to what we had in this country, as asserted by the reader of the paper, how was it that cotton machinery, with all its intricacies, could be sent to the United States, in the face of American manufacturers, even though the cost was increased from 40 to 60 per cent.? At the present time it was possible for English machinists to secure contracts for the whole of the machinery in an American mill, and inclusive of freight charges and high tariff, deliver and erect it in America at a lower cost than American engineers with all the advantages of their immeasurably superior tools were able to do. Another speaker, Mr. Barstow, ridiculed the idea that the Americans could be so pre-eminent in the manufacture of emery wheels as might be inferred from Mr. Renold, when they had before them the fact that from the neighborhood of Manchester thousands of emery wheels were every year exported to the United States.
MODERN METHODS OF QUARRYING.
Mr. Wm. L. Saunders, for many years the engineer of the Ingersoll Rock Drill Co., and hence thoroughly familiar with modern quarrying practice, read a paper before the last meeting of the American Society of Civil Engineers on the above subject, containing many interesting points, given in the Engineering News, from which we abstract as follows.
As a preliminary to describing the new Knox system of quarrying, which even yet is not universally known among quarrymen, Mr. Saunders gives the following in regard to older methods:
The Knox system is a recent invention; no mention was made of it in the tenth census, and no description has yet been given of it in any publications on quarrying. The first work done by this method was in 1885, and at the close of that year 2 quarries had adopted it. In 1886 it was used in 20 quarries; in 1887 in 44, in 1888 in upward of 100, and at the present time about 300 quarries have adopted it. Its purpose is to release dimension stone from its place in the bed, by so directing an explosive force that it is made to cleave the rock in a prescribed line without injury. The system is also used for breaking up detached blocks of stone into smaller sizes.
Quarrymen have, ever since the introduction of blasting, tried to direct the blast so as to save stock. Holes drilled by hand are seldom round. The shape of the bit and their regular rotation while drilling usually produce a hole of somewhat triangular section. It was observed, many years ago, that when a blast was fired in a hand-drilled hole the rock usually broke in three directions, radiating from the points of the triangle in the hole. This led quarrymen to look for a means by which the hole might be shaped in accordance with a prescribed direction of cleavage.
The oldest sandstone quarries in America are those at Portland, Conn. It was from these quarries that great quantities of brownstone were shipped for buildings in New York. The typical "brownstone front" is all built of Portland stone. As the Portland quarries were carried to great depths the thickness of bed increased, as it usually does in quarries. With beds from 10 to 20 ft. deep, all of solid and valuable brownstone, it became a matter of importance that some device should be applied which would shear the stone from its bed without loss of stock and without the necessity of making artificial beds at short distances. A system was adopted and used successfully for a number of years which comprised the drilling of deep holes from 10 to 12 in. in diameter, and charging them with explosives placed in a canister of peculiar shape. The drilling of this hole is so interesting as to warrant a passing notice. The system was similar to that followed with the old fashioned drop drill. The weight of the bit was the force which struck the blow, and this bit was simply raised or lowered by a crank turned by two men at the wheel. The bit resembled a broad ax in shape, in that it was extremely broad, tapering to a sharp point, and convex along the edge.
FIG. 1
Fig. 1 illustrates in section one of the Portland drills, and a drill hole with the canister containing the explosive in place. The canister was made of two curved pieces of sheet tin with soldered edges, cloth or paper being used at the ends. It was surrounded with sand or earth, so that the effect of the blast was practically the same as though the hole were drilled in the shape of the canister. In other words, the old Portland system was to drill a large, round hole, put in a canister, and then fill up a good part of the hole. Were it possible to drill the hole in the shape of the canister, it would obviously save a good deal of work which had to be undone. The Portland system was, therefore, an extravagant one, but the results accomplished were such as to fully warrant its use. Straight and true breaks were made, following the line of the longer axis of the canister section, as in Fig. 2.
FIG. 2
It was found that with the old Portland canister two breaks might be made at right angles by a single blast, when using a canister shaped like a square prism. In some of the larger blasts, where blocks weighing in the neighborhood of 2,000 tons were sheared on the bed, two holes as deep as 20 ft. were drilled close together. The core between the holes was then clipped out and large canisters measuring 2 ft. across from edge to edge were used.
In regard to another of the older systems of blasting, known as Lewising, Mr. Saunders says:
A Lewis hole is made by drilling two or three holes close together and parallel with each other, the partitions between the holes being broken down by using what is known as a broach. Thus a wide hole or groove is formed in which powder is inserted, either by ramming it directly in the hole, or by puling it in a canister, shaped somewhat like the Lewis hole trench. A complex Lewis hole is the combination of 3 drill holes, while a compound Lewis hole contains 4 holes. Lewising is confined almost entirely to granite. In some cases a series of Lewis holes is put in along the bench at distances of 10 and 25 ft. apart, or even greater, each Lewis hole being situated equidistant from the face of the bench. The holes are blasted simultaneously by the electric battery.
After noting another system used to a limited extent, and not to be commended, viz., the use of inverted plugs and feathers (the plugs and feathers being inserted as a sort of tamping which the blast drives upward to split the rock), Mr. Saunders continues in substance as follows:
It is thus seen that the "state of the art" has been progressive, though it was imperfect. Mr. Sperr, in his reference to this subject, made in the report of the tenth census, says: "The influence of the shape of the drill hole upon the effects of the blast does not seem to be generally known, and a great waste of material necessarily follows." This was written but a few years before the introduction of the new system, and it is doubtless true that attention was thus widely directed to the conspicuous waste, due to a lack of knowledge of the influence of the shape of a drill hole on the effect of a blast. The system developed by Mr. Knox practically does all and more than was done by the old Portland system, and it does it at far less expense. It can best be described by illustrations.
FIG. 3, 4, 5 and 6
Fig. 3 is a round hole drilled either by hand or otherwise, preferably otherwise, because an important point is to get it round. Fig. 4 is the improved form of hole, and this is made by inserting a reamer, Figs. 5 and 6, into the hole in the line of the proposed fracture, thus cutting two V-shaped grooves into the walls of the hole. The blacksmith tools for dressing the reamers are shown in Fig. 7. The usual method of charging and tamping a hole in using the new system is shown in Fig. 8. The charge of powder is shown at C, the air space at B and the tamping at A. Fig. 9 is a special hole for use in thin beds of rock. The charge of powder is shown at C, the rod to sustain tamping at D, air space at BB, and tamping at A.
FIG. 7
Let us assume that we have a bluestone quarry, in which we may illustrate the simplest application of the new system. The sheet of stone which we wish to shear from place has a bed running horizontally at a depth of say 10 ft. One face is in front and a natural seam divides the bed at each end at the walls of the quarry. We now have a block of stone, say 50 ft. long, with all its faces free except one—that opposite and corresponding with the bench. One or more of the specially formed holes are put in at such depth and distance from each other and from the bench as may be regulated by the thickness, strength and character of the rock. No man is so good a judge of this as the quarry foreman who has used and studied the effect of this system in his quarry. Great care should be taken to drill the holes round and in a straight line. In sandstone of medium hardness these holes may be situated 10, 12 or 15 ft. apart. If the bed is a tight one the hole should be run entirely through the sheet and to the bed; but with an open free bed holes of less depth will suffice.
FIG. 8 and 9
The reamer should now be used and driven by hand. Several devices have been applied to rock drills for reaming the hole by machinery while drilling; that is, efforts have been made to combine the drill and the reamer. Such efforts have met with only partial success. The perfect alignment of the reamer is so important that where power is used this point is apt to be neglected. It is also a well known fact that the process of reaming by hand is not a difficult or a slow one. The drilling of the hole requires the greatest amount of work. After this has been done it is a simple matter to cut the V-shaped grooves. The reamer should be applied at the center, that is, the grooves should be cut on the axis or full diameter of the hole. The gauge of the reamer should be at least 1½ diameters. Great care should be taken that the reamer does not twist, as the break may be thereby deflected; and the reaming must be done also to the full depth of the hole.
The hole is now ready for charging. The powder should be a low explosive, like black or Judson powder or other explosives which act slowly. No definite rule can be laid down as to the amount of powder to be used, but it should be as small as possible. Very little powder is required in most rocks. Hard and fine grained stone requires less powder than soft stone. Mr. Knox tells of a case which came under his observation, where a block of granite "more than 400 tons weight, split clear in two with 13 oz. of FF powder." He compares this with a block of sandstone of less than 100 tons weight "barely started with 2½ lb. of the same grade of powder, and requiring a second shot to remove it."
It is obvious that enough powder must be inserted in the hole to produce a force sufficient to move the entire mass of rock on its bed. In some kinds of stone, notably sandstone, the material is so soft that it will break when acted upon by the force necessary to shear the block. In cases of this kind a number of holes should be drilled and fired simultaneously by the electric battery. In such work it is usual to put in the holes only 4 or 5 ft. apart. The powder must, of course, be provided with a fuse or preferably a fulminating cap. It is well to insert the cap at or near the bottom of the cartridge, as shown in Figs. 8 and 9.
After the charge the usual thing to do is to insert tamping. In the improved form of hole the tamping should not he put directly upon the powder, but an air space should be left, as shown at B, Fig. 8. The best way to tamp, leaving an air space, is first to insert a wad, which may be of oakum, hay, grass, paper or other similar material. The tamping should be placed from 6 to 12 in. below the mouth of the hole. In some kinds of stone a less distance will suffice, and as much air space as practicable should intervene between the explosive and the tamping. If several holes are used on a line they should be connected in series and blasted by electricity. The effect of the blast is to make a vertical seam connecting the holes, and the entire mass of rock is sheared several inches or more.
The philosophy of this new method of blasting is simple, though a matter of some dispute. The following explanation has been given. See Fig. 10.
FIG. 11
"The two surfaces, a and b, being of equal area, must receive an equal amount of the force generated by the conversion of the explosive into gas. These surfaces being smooth and presenting no angle between the points, A and B, they furnish no starting point for a fracture, but at these points the lines meet at a sharp angle including between them a wedge-shaped space. The gas acting equally in all directions from the center is forced into the two opposite wedge-shaped spaces, and the impact being instantaneous the effect is precisely similar to that of two solid wedges driven from the center by a force equally prompt and energetic. All rocks possess the property of elasticity in a greater or less degree, and this principle being excited to the point of rupture at the points, A and B, the gas enters the crack and the rock is split in a straight line simply because under the circumstances it cannot split in any other way."
Another theory which is much the same in substance is then given, and after some general discussion of the theory of the action of the forces under the several systems, the paper continues:
The new form of hole is, therefore, almost identical in principle with the old Portland canister, except that it has the greater advantage of the V-shaped groove in the rock, which serves as a starting point for the break. It is also more economical than the Portland canister, in that it requires less drilling and the waste of stone is less. It is, therefore, not only more economical than any other system of blasting, but it is more certain, and in this respect it is vastly superior to any other blasting system, because stone is valuable, and anything which adds to the certainty of the break also adds to the profit of the quarryman.
It is doubtless true that, notwithstanding the greater area of pressure in the new form of hole, the break would not invariably follow the prescribed line but for the V-shaped groove which virtually starts it. A bolt, when strained, will break in the thread whether this be the smallest section or not, because the thread is the starting point for the break. A rod of glass is broken with a slight jar provided a groove has been filed in its surface. Numerous other instances might be cited to prove the value of the groove. Elasticity in rock is a pronounced feature, which varies to a greater or less extent; but it is always more or less present. A sandstone has recently been found which possesses the property of elasticity to such an extent that it may be bent like a thin piece of steel. When a blast is made in the new form of hole the stone is under high tension, and being elastic it will naturally pull apart on such lines of weakness as grooves, especially when they are made, as is usually the case in this system, in a direction at right angles with the lines of least resistance.
Horizontal holes are frequently put in and artificial beds made by "lofting." In such cases where the rock has a "rift" parallel with the bed, one hole about half way through is sufficient for a block about 15 ft. square, but in "liver" rock the holes must be drilled nearly through the block and the size of the block first reduced.
A more difficult application of the system, and one requiring greater care in its successful use, is where the block of stone is so situated that both ends are not free, one of them being solidly fixed in the quarry wall. A simple illustration of a case of this kind is a stone step on a stairway which leads up and along a wall, Fig. 11. Each step has one end fixed to the wall and the other free. Each step is also free on top, on the bottom and on the face, but fixed at the back. We now put one of the new form of holes in the corner at the junction of the step and the wall. The shape of the hole is as shown in Fig. 12.
FIG. 11
It is here seen that the grooves are at right angles with each other, and the block of stone is sheared by a break made opposite and parallel with the bench, as in the previous case, and an additional break made at right angles with the bench and at the fixed end of the block. Sometimes a corner break is made by putting in two of the regular V-shaped holes in the lines of the proposed break and without the use of the corner hole. A useful application of this system is in splitting up large masses of loose stone. For this purpose the V-shaped grooves are sometimes cut in four positions and breaks are made in four directions radiating from the center of the hole as shown in Fig. 12. In this way a block is divided into four rectangular pieces.
FIG. 12
Though the new system is especially adapted to the removal of heavy masses of rock, yet it has been applied with success in cases where several light beds overlie each other. In one such instance 10 sheets, measuring in all only 6 ft., were broken by a blast, but in cases of this kind the plug and feather process applies very well, and the new system, when used, must be in the hands of an expert, or the loss will be serious.
Referring again to our stone step, let us imagine a case where this stairway runs between two walls. We have here each step fixed at each end and free only on the top, the bottom, and one face. Let us assume that there is a back seam, that is, that the step is not fixed at the back. In a quarry, this seam, unless a natural one, should be made by a channeling machine. In order to throw this step put of place it must be cut off at both ends, and for this purpose the V-shaped holes are put in at right angles to the face. It is well, however, to put the first two holes next the back seam in a position where the grooves will converge at the back so as to form a sort of key, which serves a useful purpose in removing the block after the blast. In quarries where there are no horizontal beds a channeling machine should be used to free the block on all sides and to a suitable depth, and then the ledge may be "lofted" by holes placed horizontally.
Where "pressure" exists in quarries, the new system has certain limitations. After determining the line of "pressure" it is only practicable to use the system directly on the line of thrust, or at right angles to it. It is much better, however, to release the "pressure" from the ledge by channeling, after which a single end may be detached by a Knox blast. It is well to bear in mind that the holes should invariably be of small diameter. In no case should the diameter of a hole be over 1½ in. in any kind of rock. This being the case, the blocks of stone are delivered to the market with but little loss in measurement. It is a noticeable fact that stone quarried by the new system shows very little evidence of drill marks, for the faces are frequently as true as though cut with a machine.
A further gain is the safety of the system. The blasting is light and is confined entirely within the holes. No spalls or fragments are thrown from the bast.
The popular idea that the system is antagonistic to the channeling process is a mistaken one. There are, of course, some quarries which formerly used channeling machines without this system, but which now do a large part of the work by blasting. Instances, however, are rare where the system has replaced the channeler. The two go side by side, and an intelligent use of the new system in most quarries requires a channeling machine. There are those who may tell of stone that has been destroyed by a blast on the new system, but investigation usually shows that either the work was done by an inexperienced operator, or an effort was made to do too much.
A most interesting illustration of the value of this system, side by side with the channeler, is shown in the northern Ohio sandstone quarries. A great many channeling machines are in use there, working around the new form of holes, and when used together in an intelligent and careful manner, the stone is quarried more cheaply than by any other process that has yet been devised.
To a limited extent the system has been used in slate. The difficulty is that most of the slate quarries are in solid ledges, where no free faces or beds exist; but it has been used with success in a slate quarry at Cherryville, Pa., since 1888. Among notable blasts made by this system are the following: At the mica schist quarries, at Conshohocken, Pa., a hole 1½ in. in diameter was drilled in a block which was 27 ft. long, 15 ft. wide and 6 ft. thick. The blast broke the stone across the "rift," only 8 oz. of black powder being used. At the Portland, Conn., quarries a single blast was fired by electricity, 15 holes being drilled with 2 lb. of coarse No. C powder in each hole, and a rock was removed 110 ft. long, 20 ft. wide and 11 ft. thick, containing 24,200 cu. ft., or about 2,400 tons, the fracture being perfectly straight. This large mass of stone was moved out about 2 in. without injury to itself or the adjoining rock.
Another blast at Portland removed 3,300 tons a distance of 4 in. Seventeen holes were drilled, using 2 lb. of powder in each hole, the size of the block being 150 × 20 × 11 ft. In a Lisbon, O., quarry a block of sandstone 200 ft. long, 28 ft. wide and 15 ft. thick was moved about ½ in. by a blast. This block was also afterward cut up by this system in blocks 6 ft. square. A sandstone bowlder 70 ft. long, average width 50 ft., average thickness 13 ft., was embedded in the ground to a depth of about 7 ft. A single hole 8 ft. deep was charged with 20 oz. of powder and the rock was split in a straight line from end to end and entirely to the bottom. A ledge of sandstone open on its face and two ends, 110 × 13 × 8 ft., was moved by a blast about 3 in. without wasting a particle of rock, 8 holes being used, drilled by three men in just one day, and 15 oz. of powder being used in each hole. A sandstone ledge, open on the face and end only, 200 × 28 × 15 ft., containing 84,000 cu. ft. stone, was moved ½ in. by 25 holes, each containing 1 lb. of powder.
THE TROTTER CURVE RANGER.
This little instrument was exhibited in a somewhat crude state at the meeting of the British Association at Newcastle in 1889. It has since been modified in several respects, and improvements suggested by practical use have been introduced, bringing it into a practical form, and enabling a much greater accuracy to be attained. The principle is one which is occasionally employed for setting out circles with a pocket sextant, viz., the property of a circle that the angle in a segment is constant. The leading feature of the invention is the arrangement of scales, which enables the operation of setting put large curves for railway or other work to be carried out without requiring any calculations, thereby enabling any intelligent man to execute work which would otherwise call for a knowledge of the use of a theodolite and the tables of tangential angles.
FIG. 1—PERSPECTIVE VIEW OF INSTRUMENT MOUNTED ON A STAFF.
The instrument is intended to be thoroughly portable; so much so, indeed, that it is not necessary or even desirable to use a tripod. It may be held in the hand like a sextant, or may be carried on a light staff. The general appearance is shown in Fig. 1. It will be seen that a metal plate, on which two scales are engraved, carries a mirror at one end and an eye piece at the other. The mirror is mounted on a metal plate, which is shaped to a peculiar curve. A clamp and slow motion provide for rapid and for fine adjustment. The eye piece is set at an angle, and contains a half silvered mirror, the upper portion being transparent. This allows direct vision along the axis of the eye piece, and at the same time vision in another direction, after two reflections, one in the eye piece and the other at the adjustable mirror. Fig. 2 is an outline plan of the instrument when closed. In the first form of the instrument only one mirror was provided, but by the double reflection in the improved pattern, any accidental twisting of the rod or handle produces no displacement of the images, since the inclination of one mirror neutralizes the equal and opposite inclination of the other. No cross line is required with the new arrangement, since it is only necessary that the two images should coincide.
FIG. 2.—OUTLINE OF INSTRUMENT SHOWING THE PATH OF THE DIRECT AND OF THE REFLECTED RAY.
The dotted line A B represents the direct ray, and the line A C D the reflected one. Fig. 3 shows the different geometrical and trigonometrical elements of the curve, which can be read upon the various scales, or to which the instrument may be set. An observer standing at C sights the point B directly and the point A by reflection. A staff being set up at each point, he will see them simultaneously, and in coincidence if the instrument be properly set for the curve. If any intermediate position be taken up on the curve, both A and B will be seen in coincidence. If the two rods do not appear superimposed, the operator must move to the right or the left until this is the case. The instrument will then be over a point in the curve. Any number of points at any regular or irregular distances along the curve can thus be set out. One of the simplest elements which can be taken as a datum is the ratio of the length of the chord to the radius, AB/AO, Fig. 3. This being given, the value of the ratio is found on the straight scale on the body of the instrument, and the curved plate is moved until the beveled edge cuts the scale at the desired point. The figure of this curve is a polar curve, whose equation is r = a ± b sin. 2 θ, where a is the distance from the zero graduation to the axis of the mirror, and b is the length of the scale from zero to 2, and θ is the inclination of the mirror. In the perspective view, Fig. 1, the curved edge cuts the scale at 1. The instrument being thus set, the following elements may be read either directly on the scales or by simple arithmetical calculation:
FIG. 3
The radius = 1.
AB, the chord, read direct on the straight scale.
AFB, the length of the arc, read direct on the back or under surface of the plate.
FH, the versed sine, read direct on the curved scale.
ACB, the angle in the segment, read direct on the graduated edge.
EAB, the angle between the chord and the tangent, read direct on the graduated edge.
GAB, the tangential angle = 180 deg. - ACB.
AOB, the angle at the center = 2GAB.
AGB, the angle between the tangents = 180 deg. - AOB.
OAB, the angle between the chord and the radius = EAB - 90 deg.
AH2 GF = —— - FH. HO
| AH2 | ||
| GF = | —— | - FH. |
| HO |
The foregoing elements are contained in a very simple diagram, Fig. 4, which is engraved on the instrument, together with the following references:
B = 180 deg. - A.
C = 2B.
D = 180 deg. - C.
E = A - 90.
Only one adjustment is necessary, and this is provided by means of the screws which fix the inclination of the eyepiece. This is set at such an angle that the instrument, when closed and reading 90° on the divided limb, acts as an optical square.
It is not necessary, as in the ordinary method with a theodolite, that one end of the curve should be visible from the other. If an obstacle intervenes, all that part of the curve which commands a view of both ends can be set out, and a ranging rod can be set up at any point of the curve so found, and the instrument may be reset to complete the curve.
To set out a tangent to the curve at A, Fig. 3, set up a rod at A and another at any point C, and take up a position on the curve at some point between them. Adjust the mirror until the rods are seen superimposed. Then moving back to A, observe C direct, and set up a rod at E in the line observed by reflection. Then A E is the tangent required. Similarly, on completing the setting out of a curve, and arriving at the end of the chord, the remote end being seen by reflection, the direction observed along the axis of the eyepiece is the new tangent.
Any of the angles or other ratios already mentioned may be used for setting the instrument, but if no data whatever are given, as in the rough surveys for colonial railways where no previous surveys exist, it is only necessary to select points through which the curve must pass, to set up ranging rods either at the extremities of the desired curve, or at any points thereon, to take up a position on the desired curve between two rods, and to adjust the instrument until they are seen in coincidence. The curve can then be set out, and fully marked, and the elements of the curve can be read on the scales and recorded for reference.
FIG. 4.—DIAGRAM ENGRAVED ON THE INSTRUMENT.
Various other cases which may occur in practice can be rapidly met by one or other of the various scales. Suppose the angle A G B between the tangents be given, together with the middle point F on the curve, Fig. 3. Subtract this angle from 180 deg., the difference gives the angle at the center A O B. Take half this, and set the instrument to the angle thus found. Walk along the tangent until a rod set up at some point in the tangent, say E, is seen in coincidence with a rod set up at B. The position of the instrument then marks the point of departure A. A rod being placed at A, the first half of the curve may be set out; or, if B is invisible, the instrument may be reset for the angle E A B, and the whole curve set out up to B. No cutting of hedges is necessary, as with theodolite work, for a curve can easily be taken piece by piece. Inclination of the whole instrument introduces no appreciable error. If the eye piece be pointed up or down hill, the instrument is thrown a little to one side or other of the tip of the staff, but in a plane tangent to the circle. Errors made in setting out a curve with the Trotter curve ranger are not cumulative, as in the method of tangential angles with a theodolite. No corrections for inaccurate hitting of the final rod can occur, for the curve must necessarily end at that point. It should be observed that the instrument is not intended to supersede a theodolite, but it has the great advantage over the older instrument that no assistant or chains or trigonometrical tables or any knowledge of mathematics are required. The data being given, by a theodolite or otherwise, an intelligent platelayer can easily set out the curve, while the trained engineer proceeds in advance with the theodolite. No time is lost; as in chaining, since the marks may be made wherever and as often as convenient. In work where high accuracy is required this instrument is well adapted for filling in, and where a rough idea of the nature of a given curve is required, the mirror being adjusted for any three points upon it, the various elements may be read off on the scales. A telescope is provided, but the errors not being cumulative, it is rarely required. The curve ranger weighs 1 lb. 10 oz., and is manufactured by Messrs. Elliott Bros., St. Martin's Lane, London. It is the invention of Mr. Alex. P. Trotter, Westminster.—The Engineer.
THE RAIL SPIKE AND THE LOCOMOTIVE.[1]
Early in October, 1830, and shortly after the surveys of the Camden and Amboy Railroad were completed, Robert L. Stevens (born 1787) sailed for England, with instructions to order a locomotive and rails for that road.
At that time no rolling mill in America was able to take a contract for rolling T rails.
Robert Stevens advocated the use of an all-iron rail in preference to the wooden rail or stone stringer plated with strap iron, then in use on one or two short American railroads. At his suggestion, at the last meeting held before he sailed, after due discussion, the Board of Directors of the Camden and Amboy Railroad passed a special resolution authorizing him to obtain the rails he advocated.