HOW THE HOLE WAS MADE AND THE OIL BROUGHT UP.

A letter from Bradford, Pa., says: The machinery used in boring one of these deep oil wells, while simple enough in itself, requires nice adjustment and skill in operating. First comes the derrick, sixty feet high, crowned by a massive pulley.

The derrick is a most essential part of the mechanism, and its shape and height are needed in handling the long rods, piping, casting, and other fittings which have to be inserted perpendicularly. The borer or drill used is not much different from the ordinary hand arm of the stone cutters, and the blade is exactly the same, but is of massive size, three or four inches across, about four feet long, and weighing 100 or 200 pounds. A long solid rod, some thirty feet long, three inches in diameter, and called the "stem," is screwed on the drill. This stem weighs almost a ton, and its weight is the hammer relied on for driving the drill through dirt and rock. Next come the "jars," two long loose links of hardened iron playing along each other about a foot.

The object of the jars is to raise the drill with a shock, so as to detach it when so tightly fixed that a steady pull would break the machinery. The upper part of the two jars is solidly welded to another long rod called the sinker bar, to the upper end of which, in turn, is attached the rope leading up to the derrick pulley, and thence to a stationary steam engine. In boring, the stem and drill are raised a foot or two, dropped, then raised with a shock by the jars, and the operation repeated.

If I may hazard a further illustration of the internal boring machinery of the well, let the reader link loosely together the thumbs and forefingers of his two hands, then bring his forearms into a straight line. Conceiving this line to be a perpendicular one, the point of one elbow would represent the drill blade, the adjacent forearm and hand the stem, the linked finger the jars, and the other hand and forearm the sinker bar, with the derrick cord attached at a point represented by the second elbow. By remembering the immense and concentrated weight of the upright drill and stem, the tremendous force of even a short fall may be conceived. The drill will bore many feet in a single day through solid rock, and a few hours sometimes suffices to force it fifty feet through dirt or gravel. When the debris accumulates too thickly around the drill, the latter is drawn up rapidly. The debris has previously been reduced to mud by keeping the drill surrounded by water. A sand pump, not unlike an ordinary syringe, is then let down, the mud sucked up, lifted, and then the drill sent down to begin its pounding anew. Great deftness and experience are needed to work the drill without breaking the jars or connected machinery, and, in case of accident, there are grapples, hooks, knives, and other devices without number, to be used in recovering lost drills, cutting the rope, and other emergencies, the briefest explanation of which would exceed the limits of this letter.

The exciting moment in boring a well is when a drill is penetrating the upper covering of sand rock which overlies the oil. The force with which the compressed gas and petroleum rushes upward almost surpasses belief. Drill, jars, and sinker bar are sometimes shot out along with debris, oil, and hissing gas. Sometimes this gas and oil take fire, and last summer one of the wells thus ignited burned so fiercely that a number of days elapsed before the flames could be extinguished. More often the tankage provided is insufficient, and thousands of barrels escape. Two or three years ago, at the height of the oil production of the Bradford region, 8,000 barrels a day were thus running to waste. But those halcyon days of Bradford have gone forever. Although nineteen-twentieths of the wells sunk in this region "struck" oil and flowed freely, most of them now flow sluggishly or have to be "pumped" two or three times a week.

"Piping" and "casing," terms substantially identical, and meaning the lining of the well with iron pipe several inches in the interior diameter, complete the labor of boring. The well, if a good flowing one, does all the rest of the work itself, forcing the fluid into the local tanks, whence it is distributed into the tanks of the pipe-line companies, and is carried from them to the refineries. The pipe lines now reach from the oil regions to the seaboard, carrying the petroleum over hill and valley, hundreds of miles to tide-water.

A CEMENT RESERVOIR.

The annexed figures represent, on a scale of 1 to 50, a plan and vertical section of a reservoir of beton, 11 cubic meters in capacity, designed for the storage of drinking water and for collecting the overflow of a canal. The volume of beton employed in its construction was 0.9 cubic meter per cubic meter of water to be stored. The inner walls were covered with a layer of cement to insure of tightness.

A CEMENT RESERVOIR.

T is the inlet pipe, with a diameter of 0.08 m.

T' is the distributing pipe, and T" is the waste pipe.—Annales des Travaux Publics.

MACHINE FOR GRINDING LITHOGRAPHIC INKS AND COLORS.

The grinding of the inks and colors that are employed in lithographing is a long and delicate operation, which it has scarcely been possible up to the present time to perform satisfactorily otherwise than by hand, because of the perfect mixture that it is necessary to obtain in the materials employed.

Per contra, this manual work, while it has the advantage of giving a very homogeneous product, offers the inconvenience of taking a long time and being costly. The Alauzet machine, shown in the accompanying cut, is designed to perform this work mechanically.

The apparatus consists of a flat, cast iron, rectangular frame, resting upon a wooden base which forms a closet. In a longitudinal direction there is mounted on the machine a rectangular guide, along which travel two iron slides in the shape of a reversed U, which make part of two smaller carriers that are loaded with weights, and to which are fixed cast-steel mullers.

At the center of the frame there is fixed a support which carries a train of gear wheels which is set in motion by a pulley and belt. These wheels serve to communicate a backward and forward motion, longitudinally, to the mullers through the intermedium of a winch, and a backward and forward motion transversely to two granite tables on which is placed the ink or color to be ground. This last-named motion is effected by means of a bevel pinion which is keyed to the same axle as the large gear wheel, and which actuates a heart wheel—this latter being adjusted in a horizontal frame which is itself connected to the cast iron plate into which the tables are set.

This machine, which is 2 meters in length by 1 meter in width, requires a one-third horse power to actuate it. It weighs altogether about 800 kilogrammes.—Annales Industrielles.

A NEW EVAPORATING APPARATUS.

At a recent meeting of the Société Industrielle of Elbeuf, Mr. L. Quidet described an apparatus that he had, with the aid of Mr. Perré, invented for evaporating juices.

In this new apparatus a happy application is made of those pipes with radiating disks that have for some time been advantageously employed for heating purposes. In addition to this it is so constructed as to give the best of results as regards evaporation, thanks to the lengthy travel that the current of steam makes in it.

It may be seen from an examination of the annexed cuts, the apparatus consists essentially of a cylindrical reservoir, in the interior of which revolves a system formed of seven pipes, with radiating disks, affixed to plate iron disks, EE. The reservoir is mounted upon a cast-iron frame, and is provided at its lower part with a cock, B, which permits of the liquid being drawn off when it has been sufficiently concentrated. It is surmounted with a cover, which is bolted to lateral flanges, so that the two parts as a whole constitute a complete cylinder. This shape, however, is not essential, and the inventors reserve the right of giving it the arrangement that may be best adapted to the application that is to be made of it.

In the center of the apparatus there is a conduit whose diameter is greater than that of the pipes provided with radiators, and which serves to cross-brace the two ends, EE, which latter consist of iron boxes cast in a piece with the hollow shaft of the rotary system.

The steam enters through the pipe, F, traverses the first evaporating pipe, then the second, then the third, and so on, and continues to circulate in this manner till it finally reaches the last one, which communicates with the exit, G.

Motion is transmitted to the evaporator by a gearing, H, which is keyed on the shaft, and is actuated by a pinion, L, connected with an intermediate shaft which is provided with fast and loose pulleys.

The apparatus is very efficient in its action, and this is due, in the first place, to the use of radiators, which greatly increase the heating surface, and second, to the motion communicated to the evaporating parts. In fact, each of the pipes, on issuing from the liquid to be concentrated, carries upon its entire surface a pellicle which evaporates immediately.

The arrangement devised by Messrs. Perré and Quidet realizes, then, the best theoretic conditions for this sort of work, to wit:

/l 1. A large evaporating surface. 2. A very slight thickness of liquid. 3. A constant temperature of about from 100° to 120°, according to the internal pressure of the steam. l/

Owing to such advantages, this apparatus will find an application in numerous industries, and will render them many services.—Revue Industrielle.

"FLYING."

To the Editor of the Scientific American:

Your correspondent on this subject in the issue of April 14 cites an array of facts from which it would seem the proper conclusions should be inferred. I think the whole difficulty arises from a confusion of terms, and by this I mean a want of care to explain the unknown strictly in terms of the known; and I think underlying this error is a misconception as to what an animal is, and what animal strength is, only of course with reference to this particular discussion, i.e., in so far only as they may be considered physical organisms having no reference to the intellectual or moral development, all of which lies beyond the sphere of our discussion.

Purely with reference to the development of physical strength, which alone is under consideration, any animal organism whatsoever must be considered simply in the light of a machine.

A compound machine having two parts, first an arrangement of levers and points of application of power, all of which is purely mechanical, together with an arrangement of parts, designed, first, to convert fuel or food into heat, and, secondly, to transform heat into force, which is purely a chemical change in the first instance, and a transformation of energy in the second. So much for the animal—man or beast—as a machine physically considered.

What then is animal strength considered in the same light? The animal is not creative. It can make nothing—it can only transform. Does it create any strength or force? No. The strength it puts forth or exerts is merely the outcome of this transformation, which it is the office of the machine to perform.

What do we find transformed? Simply the energy, or potential, contained in the fuel or food we put into the machine. Its exact equivalent we find transformed to another form of energy, known as animal strength, which is simply heat within the system available for the working of its mechanical parts. How, then, is this energy which exists in the shape of animal strength used and distributed? This is the question the answer of which underlies this whole discussion as a principle. It is distributed to the different parts of the machine in proportion to the relative amount of physical work that nature has made it the office of any particular part to perform.

Let us see how it is with the bird machine. In course of flight he is called upon to remain in the air, which means that should he cease to make an effort to do this, i.e., should he cease to expend energy in doing it, he would fall during the first second of time after ceasing to make the effort some sixteen feet toward the center of the earth. But he remains in the air for hours and days at a time. What is he, then, doing every second of that time? He is overcoming the force of gravitation, which is incessantly pulling him down. That is, every second he is doing an amount of work equal to his weight—say 10 lb. multiplied by 16—say 160 lb. approximately; all this by beating the air with his wings. Now let us institute a slight comparison—and the work shall be performed by a man, who climbs a mountain 10,000 feet high in 10 hours. The man weighs 150 lb.; he climbs 10,000 feet; 1,500,000 foot pounds is, then, the work done. He does it in 10 hours, or 36,000 seconds, which gives an amount of work of only 42 foot pounds per second performed by his muscles of locomotion.

At the end of the ten hours the man is exhausted, while the bird delights in further flight. To what is this difference of condition due? It is due simply to the difference in the machine; but this, you say, is not explaining the unknown in terms of the known. Let us see, then, if we cannot do this. In the two accounts of work done as above cited in the case of the man and the bird, an amount of energy, i.e., heat of the system, has been expended just proportional to the work done.

Now while the bird has expended more energy in this particular work of locomotion than has the man, we find the bird machine has done little else; he has consumed but little of his available heat force in exercising his brain or the other functions of his system, or in preserving the temperature of the body, and but little of his animal heat, which is his strength, has been radiated into space. In short, we find the bird machine so devised by nature that a very large proportion of the available energy of the system can be used in working those parts contrived for locomotion, and resist the force of gravity, or, what is the same thing, nature has placed a greater relative portion of the whole furnace at the disposal of these parts than she has in man. The breast muscles of the bird are so constructed as to burn a far greater proportional amount of the fuel from which all energy is derived than do the muscles of the rest of the body combined.

Let us see how it is with the man who has climbed the mountain. In this machine we find affairs in a very different state. During his climbing he has been doing a vast amount of other work, both internal and external. His arms, his whole muscular system, in fact, has been vigorously at work, all drawing upon his total available energy. His brain has been in constant and unremitted action, as well as the other internal organs, which require a greater proportional amount of energy than they did in the bird. Besides this, he has been radiating his animal heat into space in a far greater amount. All these parts must be supplied; they cannot be neglected while the accumulated surplus is given to the machinery for locomotion or lifting. This then is what constitutes what I call the difference in the machine, which is purely one of organic development depending upon the functions nature has determined that the different organs shall perform. As for the pterodactyl quoted in the last article, I have only to remark that this discussion arose purely from a consideration of what was the best type of flying apparatus nature had given man to study, and I claim that this prehistoric bird of geology does not come within this class. For if it is not fully established that this species had become extinct long before the appearance of man on the globe, it is at least certain that the man of that early day had not dreamt of flying and was presumably content if he could find other means to evade the pterodactyl's claw.

F.J.P., U.S. Army.

THE PORTRUSH ELECTRIC RAILWAY, IRELAND.[1]

By DR. EDWARD HOPKINSON.

In the summer of 1881, Mr. W.A. Traill, late of H.M. Geological Survey, suggested to Dr. Siemens that the line between Portrush and Bushmills, for which Parliamentary powers had been obtained, would be suitable in many respects for electrical working, especially as there was abundant water power available in the neighborhood. Dr. Siemens at once joined in the undertaking, which has been carried out under his direction. The line extends from Portrush, the terminus of the Belfast and Northern Counties Railway, to Bushmills in the Bush valley, a distance of six miles. For about half a mile the line passes down the principal street of Portrush, and has an extension along the Northern Counties Railway to the harbor. For the rest of the distance, the rails are laid on the sea side of the county road, and the head of the rails being level with the ground, a footpath is formed the whole distance, separated from the road by a curbstone. The line is single, and has a gauge of three feet, the standard of the existing narrow gauge lines in Ulster. The gradients are exceedingly heavy, as will be seen from the diagram, being in parts as steep as 1 in 35. The curves are also in many cases very sharp, having necessarily to follow the existing road. There are five passing places, in addition to the sidings at the termini and at the carriage depot. At the Bushmills end, the line is laid for about 200 yards along the street, and ends in the marketplace of the town. It is intended to connect it with an electrical railway from Dervock, for which Parliamentary powers have already been obtained, thus completing the connection with the narrow gauge system from Ballymena to Larne and Cushendall. About 1,500 yards from the end of the line, there is a waterfall on the river Bush, with an available head of 24 feet, and an abundant supply of water at all seasons of the year. Turbines are now being erected, and the necessary works executed for employing the fall for working the generating dynamo machines, and the current will be conveyed by means of an underground cable to the end of the line. Of the application of the water power it is unnecessary to speak further, as the works are not yet completed. For the present, the line is worked by a small steam-engine placed at the carriage depot at the Portrush end. The whole of the constructive works have been designed and carried out by Mr. Traill, assisted by Mr. E.B. Price.

The system employed may be described as that of the separate conductor. A rail of T-iron, weighing 19 pounds to the yard, is carried on wooden posts, boiled in pitch, and placed ten feet apart, at a distance of 22 inches from the inside rail and 17 inches above the ground. This rail comes close up against the fence on the side of the road, thus forming an additional protection. The conductor is connected by an underground cable to a single shunt-wound dynamo machine, placed in the engine shed, and worked by a small agricultural steam engine of about 25 indicated horse power. The current is conveyed from the conductor by means of two springs, made of steel, rigidly held by two steel bars placed one at each end of the car, and projecting about six inches from the side. Since the conducting rail is iron, while the brushes are steel, the wear of the latter is exceedingly small. In dry weather they require the rail to be slightly lubricated; in wet weather the water on the surface of the iron provides all the lubrication required. The double brushes, placed at the extremities of the car, enable it to bridge over the numerous gaps, which necessarily interrupt the conductor to allow cart ways into the fields and commons adjoining the shore. On the diagram the car is shown passing one of these gaps: the front brush has broken contact, but since the back brush is still touching the rail, the current has not been broken. Before the back brush leaves the conductor, the front brush will have again risen upon it, so that the current is never interrupted. There are two or three gaps too broad to be bridged in this way. In these cases the driver will break the current before reaching the gap, the momentum of the car carrying it the 10 or 12 yards it must travel without power.

The current is conveyed under the gaps by means of an insulated copper cable carried in wrought-iron pipes, placed at a depth of 18 inches. At the passing places, which are situated on inclines, the conductor takes the inside, and the car ascending the hill also runs on the inside, while the car descending the hill proceeds by gravity on the outside lines.

From the brushes the current is taken to a commutator worked by a lever, which switches resistance frames placed under the car, in or out, as may be desired. The same lever alters the position of the brushes on the commutator of the dynamo machine, reversing the direction of rotation, in the manner shown by the electrical hoist. The current is not, as it were, turned full on suddenly, but passes through the resistances, which are afterward cut out in part or altogether, according as the driver desires to run at part speed or full speed.

From the dynamo the current is conveyed through the axle boxes to the axles, thence to the tires of the wheels, and finally back by the rails, which are uninsulated, to the generating machine. The conductor is laid in lengths of about 21 feet, the lengths being connected by fish plates and also by a double copper loop securely soldered to the iron. It is also necessary that the rails of the permanent way should be connected in a similar manner, as the ordinary fish plates give a very uncertain electrical contact, and the earth for large currents is altogether untrustworthy as a conductor, though no doubt materially reducing the total resistance of the circuit.

The dynamo is placed in the center of the car, beneath the floor, and through intermediate spur gear drives by a steel chain on to one axle only. The reversing levers, and also the levers working the mechanical brakes, are connected to both ends of the car, so that the driver can always stand at the front and have uninterrupted view of the rails, which is of course essential in the case of a line laid by the side of the public road.

The cars are first and third class, some open and some covered, and are constructed to hold twenty people, exclusive of the driver. At present, only one is fitted with a dynamo, but four more machines are now being constructed by Messrs. Siemens Bros., so that before the beginning of the heavy summer traffic five cars will be ready; and since two of these will be fitted with machines capable of drawing a second car, there will be an available rolling stock of seven cars. It is not intended at present to work electrically the portion of the line in the town at Portrush, though this will probably be done hereafter; and a portion, at least, of the mineral traffic will be left for the two steam-tramway engines which were obtained for the temporary working of the line pending the completion of the electrical arrangements.

Let us now put in a form suitable for calculation the principles with which Mr. Siemens has illustrated in a graphic form more convenient for the purposes of explanation, and then show how these principles have been applied in the present case.

Let L be the couple, measured in foot-pounds, which the dynamo must exert in order to drive the car, and w the necessary angular velocity. Taking the tare of the car as 50 cwt., including the weight of the machinery it carries, and a load of twenty people as 30 cwt., we have a gross weight of 4 tons. Assume that the maximum required is that the car should carry this load at a speed of seven miles an hour, on an incline of 1 in 40. The resistance due to gravity may be taken as 56 lb. per ton, and the frictional resistance and that due to other causes, say, 14 lb. per ton, giving a total resistance of 280 lb., at a radius of 14 inches. The angular velocity of the axle corresponding to a speed of seven miles an hour, is 84 revolutions per minute. Hence L = 327 foot pounds, and w = (2π × 84) / 60.

If the dynamo be wound directly on the axle, it must be designed to exert the couple, L, corresponding to the maximum load, when revolving at an angular velocity, w, the difference of potential between the terminals being the available E.M.F. of the conductor, and the current the maximum the armature will safely stand. This will be the case in the Charing-cross Electrical Railway. But when the dynamo is connected by intermediate gear to the driving wheels only, the product of L and w remains constant, and the two factors may be varied. In the present case L is diminished in the ratio of 7 to 1, and w consequently increased in the same ratio. Hence the dynamo, with its maximum load, must revolve at 588 revolutions per minute, and exert a couple of forty-seven foot-pounds. Let E be the potential of the conductor from which the current is drawn, measured in volts, C the current in amperes, and E1 the E.M.F. of the dynamo. Then E1 is proportional to the product of the angular velocity, and a certain function of the current. For a velocity ω, let this function be denoted by f(C). If the characteristic of the dynamo can be drawn, then f(C) is known.

We have then

w
E1 = ————f(1.)
Ω

If R be the resistance in circuit by Ohm's law,

E - E1
C =————
R
w
=E -—f(C)
Ω
————————
R

and therefore

Ω(E - CR)
w = ————(2.)
f(C)

Let a be the efficiency with which the motor transforms electrical into mechanical energy, then—

Power required = L w =a E1C
w
=a C—f(C)
Ω

Dividing by w,

aCf(C)
L =————. (3.)
Ω

It must be noted that L is here measured in electrical measure, or, adopting the unit given by Dr. Siemens in the British Association Address, in joules. One joule equals approximately 0.74 foot pound. Equation 3 gives at once an analytical proof of the second principle stated above, that for a given motor the current depends upon the couple, and upon it alone. Equation 2 shows that with a given load the speed depends upon E, the electromotive force of the main, and R the resistance in circuit. It shows also the effect of putting into the circuit the resistance frames placed beneath the car. If R be increased, until CR is equal to E, then w vanishes, and the car remains at rest. If R be still further increased, Ohm's law applies, and the current diminishes. Hence suitable resistances are, first, a high resistance for diminishing the current, and consequently, the sparking at making and breaking of of the circuit; and, secondly, one or more low resistances for varying the speed of the car. If the form of f(C) be known, as is the case with a Siemens machine, equations 2 and 3 can be completely solved for w and C, giving the current and speed in terms of L, E, and R. The expressions so obtained are not without interest, and agree with the results of experiment.

It may be observed that an arc light presents the converse case to a motor. The E.M.F. of the arc is approximately constant, whatever the intensity of the current passing between the carbons; and the current depends entirely on the resistance in circuit. Hence the instability of an arc produced by machines of low internal resistance, unless compensated by considerable resistance in the leads.

The following experiment shows in a striking form the principles just considered: An Edison lamp is placed in parallel circuit with a small dynamo machine, used as a motor. The Prony brake on the pulley of the dynamo is quite slack, allowing it to revolve freely. Now let the lamp and dynamo be coupled to the generator running at full speed. First, the lamp glows, in a moment it again becomes dark, then, as the dynamo gets up speed, glows again. If the brake be screwed up tight, the lamp once more becomes dark. The explanation is simple. Owing to the coefficient of self-induction of the dynamo machine being considerable, it takes a finite time for the current to obtain an appreciable intensity, but the lamp having no self-induction, the current at once passes through it, and causes it to glow. Secondly, the electrical inertia of the dynamo being overcome, it must draw a large current to produce the kinetic energy of rotation, i.e., to overcome its mechanical inertia; the lamp is therefore practically short-circuited, and ceases to glow. When once the rotation has been established, the current through the dynamo becomes very small, having no work to do except to overcome the friction of the bearings, hence the lamp again glows. Finally, by screwing up the brake, the current through the dynamo is increased, and the lamp again short-circuited.

It has often been pointed out that reversal of the motor on the car would be a most effective brake. This is certainly true; but, at the same time, it is a brake that should not be used except in cases of emergency. For this reason, the dynamo revolving at a high speed, the momentum of the current is very considerable; hence, owing to the self-induction of the machine, a sudden reversal will tend to break down the insulation at any weak point of the machine. The action is analogous to the spark produced by a Ruhmkorff coil. This was illustrated at Portrush; when the car was running perhaps fifteen miles an hour, the current was suddenly reversed. The car came to a standstill in little more than its own length, but at the expense of breaking down the insulation of one of the wires of the magnet coils. The way out of the difficulty is evidently at the moment of reversal to insert a high resistance to diminish the momentum of the current.

In determining the proper dimensions of a conductor for railway purposes, Sir William Thomson's law should properly apply. But on a line where the gradients and traffic are very irregular, it is difficult to estimate the average current, and the desirability of having the rail mechanically strong, and of such low resistance that the potential shall not vary very materially throughout its length, becomes more important than the economic considerations involved in Sir William Thomson's law. At Portrush the resistance of a mile, including the return by earth and the ground rails, is actually about 0.23 ohm. If calculated from the section of the iron, it would be 0.15 ohm, the difference being accounted for by the resistance of the copper loops, and occasional imperfect contacts. The E.M.F. at which the conductor is maintained is about 225 volts, which is well within the limit of perfect safety assigned by Sir William Thomson and Dr. Siemens. At the same time the shock received by touching the iron is sufficient to be unpleasant, and hence is some protection against the conductor being tampered with.

Consider a car requiring a given constant current; evidently the maximum loss due to resistance will occur when the car is at the middle point of the line, and will then be one-fourth of the total resistance of the line, provided the two extremities are maintained by the generators at the same potential. Again, by integration, the mean resistance can be shown to be one-sixth of the resistance of the line. Applying these figures, and assuming four cars are running, requiring 4 horse power each, the loss due to resistance does not exceed 4 per cent. of the power developed on the cars; or if one car only be running, the loss is less than 1 per cent. But in actual practice at Portrush even these estimates are too high, as the generators are placed at the bottom of the hills, and the middle portion of the line is more or less level, hence the minimum current is required when the resistance is at its maximum value.

The insulation of the conductor has been a matter of considerable difficulty, chiefly on account of the moistness of the climate. An insulation has now, however, been obtained of from 500 to 1,000 ohms per mile, according to the state of the weather, by placing a cap of insulite between the wooden posts and T-iron. Hence the total leakage cannot exceed 2.5 amperes, representing a loss of three-fourths of a horse power, or under 5 per cent, when four cars are running. But apart from these figures, we have materials for an actual comparison of the cost of working the line by electricity and steam. The steam tramway engines, temporarily employed at Portrush, are made by Messrs. Wilkinson, of Wigan, and are generally considered as satisfactory as any of the various tramway engines. They have a pair of vertical cylinders, 8 inches diameter and one foot stroke, and work at a boiler pressure of 120 lb., the total weight of the engine being 7 tons. The electrical car with which the comparison is made has a dynamo weighing 13 cwt., and the tare of the car is 52 cwt. The steam-engines are capable of drawing a total load of about 12 tons up the hill, excluding the weight of the engine; the dynamo over six tons, including its own weight; hence, weight for weight, the dynamo will draw five times as much as the steam-engine. Finally, compare the following estimates of cost. From actual experience, the steam-engine, taking an average over a week, costs—

£s.d.
Driver's wages.1100
Cleaner's wages.0120
Coke, 58½ cwt. at 25s. per ton.3131½
Oil, 1 gallon at 3s. 1d.031
Tallow, 4 lb. at 6d.020
Waste, 8 lb. at 2d.014
Depreciation, 15 per cent. on £750.233
——————
Total.£849½

The distance run was 312 miles. Also, from actual experience, the electrical car, drawing a second behind it, and hence providing for the same number of passengers, consumed 18 lb. of coke per mile run. Hence, calculating the cost in the same way, for a distance run of 312 miles in a week—

£s.d.
Wages of stoker of stationary engine.100
Coke, 52 cwt. at 25s. per ton.2150
Oil, 1 gallon at 3s. 1d.031
Waste, 4 lb. at 2d.008
Depreciation on stationary engine, 10 per cent. on £300 11s. 6d.}204
Depreciation of electrical apparatus, 15 per cent. on £500, £1 8s. 10d.
——————
Total.£5191

A saving of over 25 per cent.

The total mileage run is very small, on account of the light traffic early in the year. Heavier traffic will tell very much in favor of the electric car, as the loss due to leakage will be a much smaller proportion of the total power developed.

It will be observed that the cost of the tramway engines is very much in excess of what is usual on other lines, but this is entirely accounted for by the high price of coke, and the exceedingly difficult nature of the line to work, on account of the curves and gradients. These causes send up the cost of electrical working in the same ratio, hence the comparison is valid as between the steam and electricity, but it would be unsafe to compare the cost of either with horse-traction or wire-rope traction on other lines. The same fuel was burnt in the stationary steam-engine and in the tramway engines, and the same rolling stock used in both cases; but, otherwise, the comparison was made under circumstances in favor of the tramway engine, as the stationary steam-engine is by no means economical, consuming at least 5 lb. of coke per horse-power hour, and the experiments were made, in the case of the electrical car, over a length of line three miles long, which included the worst hills and curves, and one-half of the conductor was not provided with the insulite caps, the leakage consequently being considerably larger than it will be eventually.

Finally, as regards the speed of the electrical car, it is capable of running on the level at the rate of 12 miles per hour, but as the line is technically a tramway, the Board of Trade Regulations do not allow the speed to exceed 10 miles an hour.

Taking these data as to cost, and remembering how this will be reduced when the water power is made available, and remembering such considerations as the freedom from smoke and steam, the diminished wear and tear of the permanent way, and the advantage of having each car independent, it may be said that there is a future for electrical railways.

We must not conclude without expressing our best thanks to Messrs. Siemens Bros. for having kindly placed all this apparatus at our disposal to-night, and allowing us to publish the results of experiments made at their works.

[1]

A paper recently read before the Society of Arts, London.

THE THOMSON-HOUSTON ELECTRIC LIGHTING SYSTEM.

The generator is known as the "Thomson spherical," on account of the nearly spherical form of its armature, and differs radically from all others in all essential portions, viz., its field magnets, armature, and winding thereof, and in its commutator; both in principle and construction, and, besides, it is provided with an automatic regulator, an attachment not applied to other generators. The annexed view of the complete machine will convey an idea of the general appearance and disposition of its parts.

The revolving armature which generates the electrical current is made internally of a hollow shell of soft iron secured to the central portion of the shaft between the bearings, and is wound externally with a copper conducting wire, constituting three coils or helices surrounding the armature, which coils are, however, permanently joined, and in reality act as a single three-branched wire.

This wire, being wound on the exterior of the armature, is fully exposed to the powerful magnetic influence of the field poles, which inclose the armature almost completely. The armature will thus be seen to be thoroughly incased and protected, at the same time that all the wire upon it is subject to a powerful action of the surrounding magnets, resulting in an economy in the generation of current in its coils. The form of the armature being spherical, very little power is lost by air friction, and no injury can occur from increased speed developing centrifugal force. The field magnets, which surround the armature, are cast iron shells, wound outside with many convolutions of insulated copper wire, and are joined externally by iron bars to convey the magnetism. These outer bars serve also as a most efficient protection to the wire and armature of the machine during transportation or otherwise. Objects cannot fall upon or rest upon the wire coils and injure them. The coils of wire upon the field magnets surround not only the iron poles or shells, but are situated also so as to surround likewise the revolving armature, and increase the effect produced in it by direct induction and magnetism. This feature is not used in any other generator, nor does any other make use of a spherical armature. The shaft is mounted in babbitted bearings of ample size, sustained by a handsome frame therefor, and is of steel, finely turned and perfectly true. The shaft and armature together are balanced with the utmost care, and run without buzz or rumble. The armature wire is kept cool by an active circulation of air over its whole surface during revolution. The commutator, or portion from which the currents developed in the armature are carried out for use, is a beautiful piece of mechanism. It is mounted upon the end of the shaft, and has attached to it the wires, three only, coming from the armature wire through the tubular shaft.

The commutator is peculiar, consisting of only three segments of a copper ring, while in the simplest of other continuous current generators several times that number exist, and frequently 120! segments are to be found. These three segments are made so as to be removable in a moment for cleaning or replacement. They are mounted upon a metal support, and are surrounded on all sides by a free air space, and cannot, therefore, lose their insulated condition. This feature of air insulation is peculiar to this system, and is very important as a factor in the durability of the commutator. Besides this, the commutator is sustained by supports carried in flanges upon the shaft, which flanges, as an additional safeguard, are coated all over with hard rubber, one of the finest known insulators. It may be stated, without fear of contradiction, that no other commutator made is so thoroughly insulated and protected. The three commutator segments virtually constitute a single copper ring, mounted in free air, and cut into three equal pieces by slots across its face. Four slit copper springs, called commutator brushes or collectors, are allowed to bear lightly upon the commutator when it revolves, and serve to take up the current and convey it to the circuit. These commutator brushes are carried by movable supports, and their position is automatically regulated so as to control the strength of the developed current—a feature not found in other systems. This feature, as well as the fact that the commutator can be oiled to prevent wear, saves attendance and greatly increases the durability of the wearing surfaces, while the commutator brushes are maintained in the position of best adjustment. The commutator and brushes, in consequence, after weeks of running, show scarcely any wear.