Pneumatic Railway.

FOR THE JOURNAL OF THE FRANKLIN INSTITUTE.

A very warm controversy has been carried on in the pages of the London Mechanics' Magazine, in relation to the pneumatic railway recently patented by our countryman, Mr. Pinkus, now a resident of London. To give the readers of this journal an idea of the nature of this patent, a cut is subjoined, representing a section of the tunnel forming the railway, and showing the carriage to be propelled in its connexion with the tunnel.

The method of propulsion is by rarifying the air in the conduit pipe in front of the shield o, which is supposed to move air tight. The pressure of the air behind the shield will then urge it forward. This shield, or as

Mr. Pinkus terms it, "dynamic traveller," is connected with guide wheels mm, which keep the bar S L in the axis of the tube. To this bar is connected an upright arm, p, passing through a slit in the upper side of the pipe or tunnel, and intended to transmit the motion of the shield, lo, to the car, V V. The slit thus required in the upper side of the tunnel is closed by a

"square cord," shown in the figure, E E E, passing over one and under two wheels; the middle wheel lifting the rope as the carriage, V V, proceeds, and the front wheel guiding it to its place upon a groove made to receive it, and thus closing the slit. The car, V V, or "governor," as it is termed in the specification of the patent, moves upon two rails, attached one to each side of the tunnel, and parallel to its axis.

Mr. Pinkus claims, as new, these various arrangements, with minor ones not described, and disclaims, as old, the use of the tunnel as a means of transport for goods, &c. in its interior.

The prospectus of "a National Pneumatic Railway Association" was accompanied by the opinions of Dr. Lardner and Prof. Faraday in regard to this means of locomotion. The opinion of the former gentleman was decidedly favourable. The practicability of the scheme he does not doubt. Considers it a frictionless mode of transferring power to a distance. Calculates the necessary rarifaction to be produced in the tube or tunnel, and the power obtained. The relative economy of this new, and of the old railway. The diminution of accidents to cars, and upon inclined planes. Examines the difficulties of keeping the tunnel air tight, and concludes that they are not insurmountable.

Mr. Faraday modestly remarks, that he possesses no practical experience in regard to railways, but approves, in general, of the principles of the pneumatic railway, and enumerates some advantages which will accrue from its substitution for those of the ordinary kind.

The editor of the Mechanics' Magazine, notwithstanding the weight of authority thus against him, contends, that both in theory and practice, this

project is to be condemned, and quotes the experiments of Papin and others to show that air is not to be passed through tubes without friction, He refers, also, to the unsuccessful attempts of Valance to press air through a tunnel. These and other experiments to the same purport, the reader will find in vol. ix. of this Journal. A committee of the Institute reported upon a plan identical in principle with that of Mr. Pinkus, and the table drawn from the best experiments on the resistance of air to motion through tubes, shows how much power would be consumed in producing a given effect in a tunnel of a given length.

Here the view is taken, that the operation of drawing the air out of a tube, is of the same nature with that of forcing it in.

But on the contrary, Mr. Pinkus, in a reply to the editor of the Mechanics' Magazine, states that Mr. Hague has succeeded in applying the principle of Papin to communicate power to the distance of even seven miles, and that in one of his works, the power of a seventy horse steam engine is transmitted undiminished, and instantaneously, through a tube three miles in length. He further states, that the gas for lighting Birmingham is brought seven miles through pipes, with but a small diminution of force. Of the apparatus of Mr. Hague we have heard for the first time, but must remark that the latter fact is in contradiction to all the experiments hitherto made on the passage of gas.

The readers of this Journal would probably not be interested in the personalities of the articles in relation to this subject, and they have before them the means of forming a correct conclusion as to the merits of the pneumatic railway.

As one of the readers, I cannot approve of the scheme either in theory or practice. Not in theory, because of the consumption of power required to rarify the air in a long tube. Not in practice, from the primary difficulty of the long, uniform cylinders or tunnels required for the motion of the piston; and the secondary one, of the improbability of an air tight joint resulting from the “ square cord" and groove.

B.

Query in relation to the appropriate colour for the covering of the pipes of Condensers used in the manufacture of Gas.

TO THE COMMITTEE ON PUBLICATIONS.

Gentlemen,-Allow me to request from any one of your correspondents a reason why the pipes used for condensers at the Philadelphia Gas Works, are painted white. I understand their object to be to expose the gas as it comes from the retorts to the cooling action of the air. If so, the metal should be covered with some dark coloured paint, which, radiating better than the white, will keep the metal cool, and thus more effectually cool the gas. I take it for granted that the iron of the pipes forming the condenser must be coated to keep it from the effects of the weather, and if I am right in regard to the philosophy of the matter, the engineer is wrong. Yours, &c.

Substitute for a Waste Cock to Hy lrants. By ROBERT CORNELIUS.

K.

It is well known, that to prevent the freezing of water contained in the pipes of our hydrants, a waste cock has been applied to the lower part o the pipe through which water is drawn. This cock is opened by the same

operation which closes the escape pipe. The water from the escape pipe issues out, therefore, and passes into the ground.

Newton's patent hydrant conveys the waste water to a box, and remedies the inconvenience occurring from the process just alluded to.

h

a

The invention of Mr. Cornelius is to effect the same object. His arrangements, as explained at the last conversation meeting of the Institute, will be understood by referring to the annexed diagram. The parts are not there disposed as they will be in practice; the apparatus would want compactness in this form: they are displayed for the sake of explanation. The box, A, is connected with the top of the hydrant, and B is placed below the ground so far as to prevent the water in it from freezing. The pipe, a b, is connected, near a, with the branch pipe, k, from the main water pipes, and at b, with the upper part of the box, A. The stop cock, c, opens or closes at pleasure the end, a, of the pipe, a b. This cock has two passages, one opening from k to a b, the other, through to B. When one of these is open the other is closed, and vice versa. It is connected by the rod, c d, with the cock, d. When water is to be drawn, these cocks are brought into the position shown in the figure, when c is open and d closed; the water flows through c, and rises into the tube, a b, filling the box, A. The stop cock, d, being closed, the air from A passes by the tube, e f, into B, and escapes through g h at i. When the water has risen above the mouth, e, of the tube, ef, e being near the top of the box, A, it flows through ef into B. At first the compressed air in B finds a vent through g h, but soon the water rising above g, seals the pipe, g h, and the air is compressed in the upper part of B, until the elastic force is equal to that which the head of water can produce. The water in B meanwhile rises in g h, and at length escapes at i. When the hydrant is to be stopped, the cock, d, is torned. The same turn which opens d, closes the passage from k through c to a b, and opens that betwen ab and B. The cock, d, being open, the water from the box, A, flows out at i. The air in B passes through the pipes, a b and ef, into A, and the water which is in g h, and with any which may not be carried by the air through a b, descends into the box, B. The dimensions of the boxes, A and B, being duly regulated, and the pipes, h g and ef, properly placed, this hydrant will be very efficacious.

The quantity of water contained in the upper box, A, must flow from the bydrant after the stop cock, d, has been turned.

Civil Engineering.

Report, to the President and Directors of the Sandy and Beaver Canal Co., By E. H. GILL, Civil Engineer, and Chief Engineer of the Sandy and Beaver Canal.

GENTLEMEN,-In compliance with your request, I have the honour to lay before you the following report of the present state of the work under my direction:

During the past summer the whole line has been minutely traced, with a view to a permanent location: by this survey the total extent of canal has

been reduced three miles, or the distance from the Ohio river at the mouth of Little Beaver creek to the western termination at the Ohio canal, by the recent examination and location will not exceed seventy three and a half miles.

The Eastern division of the canal, extending from the Ohio river to a point two miles west of New Lisbon, embraces a distance of about twentyseven miles, of which seventeen miles are "slackwater:" for this description of improvement the stream is exceedingly well adapted, the valley being narrow and the banks bold and prominent, affording numerous and eligible sites for the locks and dams, and an abundance of good materials for their formation.

The summit or middle division is about fourteen and a half miles in extent, and the Western division, terminating at the Ohio canal, about thirtytwo miles. The latter division extends through a country affording the greatest facilities for constructing a cheap and permanent improvement; the valley of the creek is broad and has nearly a uniform declivity from its source to its confluence with the Tuscarawas. On the Eastern division the lockage is four hundred and sixty-four feet, and on the Western two hundred and five, constituting in all six hundred and sixty-nine feet. In locating the Western division, the level has been kept up from Williams' mill dam to the debouch into the Ohio canal at the flourishing town of Bolivar, by which arrangement an excellent water power is secured to the Company, affording a head and fall of twenty-six feet: the owners of the property at the site selected for using the water have liberally ceded to the Company ten acres of very valuable land for that purpose. Sandy Creek at that point will yield a sufficiency of water, independent of the requisite supply for the canal, at all times to work twenty, and for eight months in the year fifty pairs of mill stones. This power may reasonably be estimated as worth $6000 per annum. Many other valuable sites for hydraulic purposes have been created or purchased along the route, which, in conjunction with the one above mentioned, will probably afford the Company a revenue of $7000 per year.

On the Eastern division of the line, forty-nine sections, or twenty-four and a balf miles of canal, thirteen dams, and forty-six locks, are now under contract: on the Middle division, twenty-one sections or eleven miles, including the tunnels and the reservoir mounds on the west fork of Little Beaver Creek and Cold Run: and on the Western division twenty-eight sections or fourteen miles, eleven locks, one dam, and the aqueduct over the Tuscarawas river, constituting in all forty-nine and a half miles of canal, fourteen dams, fifty-seven locks, one aqueduct, aud two reservoir mounds now under contract.

The work has been prosecuted in most cases with energy, and is now in a greater state of forwardness than could reasonably have been anticipated, considering that the season was far advanced when it was commenced. About thirty-four sections or seventeen miles of canal are now completed, and likewise the mason work of two locks, and 144,000 cubic yards of excavation removed from the summit deep cuts: dam No. 2, on the Western division, will probably be completed next week.

The foundations of five other locks and two dams are laid, and 1500 perches of wall built; and a large quantity of stones and other materials for the construction of locks and dams is prepared and on the ground; and I have no doubt all the work now under contract, excepting the tunnels and aqueduct, will be finished in the approaching year.