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The tube as proposed is large enough for the passage of carriages of the present ordinary construction, and to avoid the objections to the use of locomotives in a tube of so great a length, it is proposed to work the traffic by pneumatic pressure. The air will be exhausted on one side of the train and forced in on the other, and so the required difference of pressure will be given for carrying the train through at any determined speed. Powerful steam-engines, for exhausting and forcing the air into the tube, will be erected on shore at each end. This system of working the traffic will secure a constant supply of the purest air. By this: system of working there would scarcely exist the chance of accident- no collision could take place. There would never be foul air within the tube. The pneumatic system can be as cheaply worked, and be in every way preferable to locomotive power. Combined goods and passenger trains might be sent through the tube at 20 miles an hour, with occasional express trains at 30 miles an hour. The estimated cost of the whole undertaking is 8,000,000 pounds. Mr. Chalmers estimates the total annual revenue at 1,300,000 pounds. The working expenses would be amply covered by 150,000 pounds, leaving about 14 or 15 per cent. dividend.
Mr. Bidder remarked that this subject had not been without interest to him, as it would be recollected that he made a few remarks on it when presiding over the section at Norwich last year. The atmospheric system, which was a very old subject, and which had been tried to a very great extent in this neighborhood, failed on account of using a small tube with a large pressure, but it was different with a large tube. He believed the pneumatic principle was the only one that could be adopted to work the tunnel. He thought there would be a difficulty in getting the united actions of the two governments to carry out the work. Unless the tunnel was worked pneumatically, he would rather cross in the present boats. Until an experiment had been made to test this plan, and the probable cost, it would be more reasonable to construct a huge breakwater, and build vessels that should be adapted to cross, except on special occasions, with certainty and dispatch.
Mr. C. Vignoles believed that if ever there was to be a tunnel to Calais it must be on this principle. The real cause of the failure of the atmospheric system was not as Mr. Bidder put it, but from an accumulation of heat in the air-pumps. It would never pay as a commercial undertaking, as there was not sufficient traffic; but it might be done by the governments. They, as engineers, considered the scheme a practical one; but he was afraid it must be left to the next generation to carry out.
Mr. Bateman, in reply, contended that the cost would not exceed his estimate.
MT. WASHINGTON RAILWAY.
The depot is 2,685 feet above the level of the sea, or 1,117 feet above the White Mountain House. This leaves a grade of 3,600 feet to be overcome, as the height of the mountain is 6,285 feet
above the level of the sea. The length of the road is two miles and thirteen-sixteenths.
The heaviest grade is 13 inches to the yard, and the very lightest, one inch to the foot. A part of the course is Jacob's Ladder," the zigzag portion of the old bridle-path lying just above the point where the trees are left behind. The railroad takes a generally straight line, however, curving slightly, only to maintain a direct course.
The locomotive pushes the car before it up the incline, and both run upon three rails, the centre one being a cog rail. The engine and car are kept upon the track by friction rollers under the side of the cog rail, and the appliances for stopping the descent are ample. By means of atmospheric brakes either the car or engine could be sent down alone at any given rate, fast or slow, and there are also hand brakes operating with equal directness upon the central wheels, together with other means of governing the machinery of locomotion. Every competent person who has examined the road and the running machinery pronounces both as safe as they could possibly be made. The landing-place at the top of the mountain is directly in the rear of the telegraph office, and but a few rods from the door of the Tip-Top House.
ELECTRICITY AND RAILROADS.
On the railroads in France electricity is taking the place of human watchfulness. On many lines there are contrivances where the passing of a train is automatically announced to neighboring stations. The cars pass over connecting wires, and the train records itself before and behind, so that its progress and appearance are alike indicated.
WHY DO RAILWAY CARRIAGES OSCILLATE?
There is so prevalent an idea that the unpleasant, and, to the nervous, injurious oscillation of railway coaches is due to the axles being too wide for the line, that the following explanation given in the “ Times,” by Mr. Charles Fox, is of much importance, both to the public and the “ companies:
“ The oscillation of railway trains, more especially at high velocities, producing what is ordinarily called .gauge concussion,' is a very serious source of wear to the permanent way and rolling stock of railways, and as a consequence, of great expense, to say nothing of the discomfort it occasions to passengers, and is, in my opinion, caused, in very great measure, by the use of wheels the tires of which are portions of cones instead of cylinders.
“ It is well known to engineers that the tires of railway-wheels are generally coned to an inclination of one in 20. It is considered that these were first introduced by Mr. George Stephenson, in the expectation of facilitating the passage of vehicles round curves, by their adapting themselves, through their various
diameters, to the different lengths of the two rails on which they were running. This, however, is not the case in practice, as any one will find upon carefully investigating the matter, inasmuch as, in a vehicle passing round a curve, the flange of the off fore wheel will be found close up to the outer rail, while that of the aft near wheel will be found running with its flange close up to the inner one, so that no benefit whatever accrues from the use of the cone, even in going round curves.
“The question of passing with steadiness over straight lines seems to have been altogether overlooked in the introduction (-2 coned wheels, for it will be obvious that with the inch play! allowed between the tires and the rails, unless one-half of such play be constantly preserved on each side of the way, two wheels staked upon the same axle will be running upon different diameters, and, consequently, a struggle arises which cannot fail to result in oscillation, inasmuch as the moment one of the flanges touches a rail, that wheel, becoming larger than the opposite one, turns it off from the rail, only to make the opposite one perform, in its turn,
same operation, when serious oscillation is the result.
“ As I have already stated, no advantage is found to arise in the use of conical wheels in passing round curves, and as much evil results therefrom, on straight lines, I have constructed upvard of 250 miles of railway abroad, in the rolling stock of which I have departed from the usual form of wheel, and have used only cylindrical ones, and have, as I expected, been gratified with the satisfactory reports I have received of the steadiness of trains supplied with them.
• Now that main-line companies are running their express trains at such high velocities, this oscillation is becoming a very serious matter, not only as a question of safety, but also one of great discomfort to the passengers, to say nothing of the enormous cost occasioned by this destructive action. I would, therefore, venture to recommend, that should any one desire to test the correctness of the principles here stated, he should select a carriage known to be most subject to oscillation, and place under it 4 cylindrical instead of conical wheels, and let this carriage run in an express train, care being taken to avoid the oscillation of the two adjoining carriages with conical wheels being communicated to it, which would be effected by the introduction of two coupling links, say 10 feet long, instead of the shorter ones in general use, and he will at once perceive the advantage of using cylindrical wheels."
THE USE OF COUNTER-PRESSURE STEAM IN
ENGINE AS A BRAKE.
M. L. De Chatelier gives the history of the improvement as follows:
“About the middle of 1865, when first I thought of organizing a system of experiments for removing the difficulties of reversing the steam, I began by trying whether it would be possible to
work the engine for any considerable time by means of the compressed-air apparatus of M. de Bergue. I soon convinced myself that the heating of the cylinders went on so rapidly that this system was inapplicable for any length of run. It was then that I drew up a complete programme of experiments, the sum and substance of which was to establish a communication between the boiler and the lower end of the exhaust-pipe, in order to supply there a jet of steam or of water, and to force into the boiler the elastic fluids, - steam or gases discharged from the cylinders by the return stroke of the piston. I pointed out three combinations to be experimented on in succession, according to the greater or less difficulty found in completely cooling the cylinders.
“ 1st. Injection of steam mixed with air.
“ 2d. Injection of steam in sufficient excess to prevent the entrance of air.
“ 3d. Injection of water, instead of steam.
“ At first I supposed that the steam would carry along with it a sufficient quantity of water to absorb the heat produced, and that it would be condensed before reaching the cylinders. This idea was incorrect. During the working with steam reversed, the water ceases to be in a state of violent ebullition, and is only carried over in small quantities; and, besides, when the steam expands in issuing from the boiler, it dries, and the small quantity of water brought with it is almost entirely converted into steam.
“ The first experiment with a mixture of steam and gases drawn into the cylinders did not give favorable results. With the injection of an excess of steam - a system which I characterized as an inverted steam engine more satisfactory results were obtained, and it was found possible to work with a moderate admission of steam with light loads on moderate gradients, without burning the packings, and without injuring the rubbing surfaces. We have in France the example of a railway on which 200 engines have only a cock for the injection of steam, and the substitution of this for the gases drawn from the smoke-box has proved sufficient to render the counter-pressure steam applicable for stopping and shunting in stations, and for moderating the speed in the descent of goods trains on gradients of one in 260. Indeed, the injection of steam alone has been effectually applied to light trains on a short incline of one in 22.
“But experience soon showed that the only general and complete solution of the question is found in the injection of water. To . complete the absorption of the heat produced by the compression in the cylinders, to force back the steam into the boiler, and to render the reversal of the steam an absolutely innocuous operation, water is the only appliance.
“When we speak of injecting water issuing from the boiler into the cylinders of a locomotive engine, it must be borne in mind that it is not water in the state in which it would flow from a fountain; it is at a high temperature when it issues from the boiler, and rushes into space at atmospheric pressure. It enters at once into ebullition, and becomes steam at 100° C., in quantity corresponding to the heat employed.
“ The new system of reversing steam has been, until recently, limited to the use of a mixture of steam and water. The engineers to whom I had entrusted the task of making the first trials followed my instructions with some apprehension, endeavoring as much as possible to avoid the injection of water into the cylinders. The result has been that, even now, in Spain, where these first trials were made, the use of counter-pressure steam has not had the success which it has had elsewhere. In France, the part played by the water was better understood; it has been abundantly injected, and the results have been most satisfactory; but up to the moment when I had an opportunity of personally experimenting, in order to verify the correctness of my first concep, tions, steam was universally considered as a necessary agent, and was used in a greater or less proportion. It was supposed that its function was to fill the cylinders during the period of aspiration, and that it served as the vehicle for the water which was shut in with it, behind the piston, at the moment the period of cushioning and forcing back commenced. It was supposed that the water led from the boiler was applied directly to the absorption of heat.
I have shown that the water is converted into steam from the moment that it enters the cylinder, even during the period of aspiration, and the conclusion is that not only is it not required to take steam directly from the boiler, but that the addition of steam to the water, beyond a certain limit, might become prejudicial.
“In every case the substitution of steam for, or the addition of steam to, water results in a discharge of a less moist steam from the cylinders into the boiler, and it is the same with the steam in the exhaust-pipe used for aspiration. The rubbing surfaces are therefore drier, and the friction greater. The more the proportion of steam is increa ed, the more these effects become sensible. At last the steam actually diverts the water indispensable for the absorption of the heat, although large quantities of steam escape by the funnel, and although no gases from the smoke-box get into the cylinders.
“ The intervention of steam during the working with inverse admission, unless required for some particular purpose, which I shall point out presently, is always more or less prejudicial. The rule, in fact, should be, to add the least possible quantity of steam to the water. The wet steam, on the water issuing from the boiler, gives this minimum proportion.
“ The apparatus to be fitted to the locomotive, to admit of working counter-pressure steam as a brake, is as simple as the principle itself. It consists of a tube of an inch to an inch and a quarter in diameter, -one inch diameter is very convenient, — which communicates between the boiler and the exhaust-pipe, and a distributing cock by which the driver regulates the supply. If, as I advise, although it is not indispensable, it is desired to have the power of injecting water and steam alternately or simultaneously, a second cock is placed, with a short tube as a branch from the first, at a short distance from its origin. The one tube enters