AB CD is a cylinder, turning upon the centre, whose shaft lies horizontally, which causes the vertical revolution of the cylinder. ZZ', a flat circular plate, cast upon the axis, and at the same time as the cylinder; m and n, holes through the plate, which open into the pipes m C'E-n B F, and are carried along the side of the cylinder and enter the caps E and F, that are firmly bolted upon the ends of it. P, the solid piston, of considerable size, which acts by its weight in the following manner :

In the drawing the end F is represented as going downwards by the weight of the piston P, which was forced up to the upper part of the cylinder, and retained there by the steam, which entered by the steam-pipe m C'E. When the piston arrives at the lowest point, the steam is let off by the steam-pipe mC'E, and admitted upon the under-side of the piston (before the upper-side), and the piston is again forced upwards, and the cylinder carried forwards by the weight of the piston. This engine passes the centres by the momentum of the machine, and is therefore not a continuous rotary-engine, but might easily be made so by the addition of another cylinder, placed at right angles to it. If the cylinder had stops applied at each end for retaining the piston when forced to the upper end, the steam might be worked

three times over, if high-pressure steam was applied at first; for the steam just sufficient for forcing up the piston might be let off into another cylinder of equal capacity, and about as much more power would be acquired; and after that the steam might be applied to a condensing-engine, when the power would be to the steam consumed as 1 to 23. At first sight it would appear that the engine would be knocked to pieces by the violent motion of the heavy metallic piston, and the force with which it must strike the end-caps. Upon examination, however, it will be seen, that no danger need be apprehended from that circumstance, as the steam might be admitted gradually, and not suddenly, as the slides usually do; besides that, the steam might be cut off as soon as the piston had moved through half the length of the cylinders, and then be allowed to act by its expansion, which would be much too weak to raise the piston, when the cylinder has considerable elevation, and would only reach the end of the cylinder by the time that it had got an inclination of 45 or 50 degrees; and, consequently, the motion of the piston towards the ends would be very gradual.

EXPERIMENTS WITH THE DIVING-BELL.

By Thomas Steele, Esq. M.A., Magdalen College, Cambridge.

In 1826 we gave an account of a Communicating Diving Bell, invented by our esteemed friend and correspondent, Mr. Steele.

It consists, as some of our readers may recollect, of two compartments in

combination; one of them, the common diving-bell, open at the bottom, the other a close chamber, with a bottom, called by the inventor, "the communicating chamber." The latter is supplied with air by pipes reaching above water, and is separated from the former by a partition, in which is set a small circular window of great thickness and strength, but so

transparent as to admit of a person in one chamber seeing distinctly through into the other. Mr. Steele has recently projected some important improvements in this apparatus, a full description of which, from his own pen, we hope in a week or two to be able to lay before the public, With the view, in the meanwhile, of preparing the reader to appreciate duly the value of these improvements, we now propose to give, in a somewhat abridged form, an account of those diving-bell experiments which have given Mr. Steele a practical knowledge of those difficulties which it has been his study to obviate, and which, if we are not greatly mistaken, he has obviated successfully. We extract it from the Appendix to Mr. Steele's" Practical Suggestions on the General Improvement of the Navigation of the Shannon."

Narrative of Circumstances which led to the Invention of the Communicating Diving Bell.

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Some years ago, I saw, lying near the harbour at Portsmouth, the Diving-bell which had been made use of by the late Mr. Thompson, when he descended upon the Royal George, sunk at Spithead ; he called it his Bell of Observation, and it was calculated for no other purpose, as it was a close vessel. It was about six and a half or seven feet high, and of a form very like a grape-jar. There was a water-tight circular cover that screwed into the top, and there were five small circular eyes" (little windows of strong glass) of about four inches in diameter, in the circumference of the part where it swelled; and across each of these there was a small bar on the outside, to prevent fracture by impinging while under water upon any hard substance. There were two flexible tubes inserted into the cover by water-tight screws, and through these the engineer, when he descended, was supplied with air, and also held conversation with the persons above water. My curiosity was excited, and I went to Gosport to find out the person, who I was informed had been in the habit of at. tending upon deck when the bell was under water, to receive orders from below, and have them carried into execution. He gave me a great deal of very interesting information, and particularly gave me assurance of the distinctness with which the voice could be heard from under water, and conversation carried on

through the tube, which was called the trumpet; the second tube was called the air-pipe. The man's name who gave me this information is Wood, and I believe he now works at a shipwright's at Fareham.

In the year 1825 I made, for the first time, as a matter of curiosity, a descent in a common working-bell, of course open at the bottom. While I was under water, I was more occupied in making observations on what I saw than in deducing consequences; but after ascending, it suddenly occurred to me, that I could make a great improvement in divingbells, by combining with the common working-bell the bell of observation; for

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I suppose there was a little window in the bell in which I was down, what would there be to prevent Thompson from looking into it from his bell, and telling what he saw ?"

Let me, therefore, suppose the two bells to approximate until they coalesce, and have a common side and commou window; the engineer in the bell of observation, sitting without pressure from condensed air, and quite at ease, no matter at what depth the bell may be working, will look into a little submarine illuminated chamber (the bell in which I descended had been illuminated by a lantern); will see every thing that is doing, and hold conversation with the persons above water.

Thinking one evening afterwards of the violent strain on the chain of suspension, and the consequent danger, when the bell emerging, ceases to have any support from the water; I set myself to work, to find out some method of getting the men out unwet, without the necessity of raising the bell itself out of the water.

A mode of doing this theoretically possible, quickly suggested itself to me; but one which, in practice, would call to memory the story in Peregrine Pickle, of the gentleman who was remarkable for great mechanical inspiration, and had invented a beautiful machine for cutting cabbages; to the general use of which, however, there was a practical objection, by no means unimportant, namely, that it required the aid of a man and a horse to work it in the cabbage-bed.

This theoretical non-impossibility, was as follows: Suppose the bell (I mean the common working-bell) to be brought to rest upon a ledge, or little platform, projecting horizontally under water from the side of the ship; suppose a tube, of a diameter of something less than a yard, bent at an angle, and one leg so much longer than the other, that while the extremity of the shorter leg

was placed under, and in contact with the platform, the extremity of the longer one should be above water. Now, imagine the shorter leg to be not merely in contact with, but to be united with the platform. Let us now suppose a circular hole in the platform over the tube, with an air-tight cover; and let us suppose the longer leg to terminate above water, in an air-tight chamber, with an air-tight door. Now it is quite evident, that if the air-chamber and the tube be filled by a condensing air-pump, with air as highly condensed as the air in the bell while it rests upon the platform, the circular cover might be unscrewed, and that the workmen might first descend into the short leg, and then ascend through the long one into the chamber above, and so walk out dry upon deck, without taking the bell out of the water.

This, however, as I have said, was mere theorizing. An improvement, however, possible and practically useful, was the result of this theoretical non-impossibility for it immediately suggested to me an air-tight chamber on deck, with windows in it like the bell of observation, and connected by a flexible tube with the working-bell; and so gave, as an immediate consequence, a second mode of communicating," by conver sation with the persons below.

Experiments with the Communicating Diving Bell-Related by a Friend of Mr. Steele's.

The inventor, before descending, placed a lighted lantern in the open compartment; he next entered the communicating chamber, through a circular aperture, which was firmly screwed down upon him; and he then gave orders to be lowered under water.

In this descent, the water was prevented from entering the open bell by the ordinary operation of the condensing airpump upon deck; and Mr. Steele had, consequently an opportunity of observing every thing within it strongly illuminated by the lantern; while, at the same time, instead of being obliged to endure the pressure of condensed air, and to depend upon signals by strokes of a hammer, he sat at his ease in air of no greater density than that of the atmosphere, and conversed through one of the pipes with his friends above water.

While he remained down, he described what he saw in the open bell, and gave such directions as circumstances rendered necessary. During this time, by simply

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turning a cock, he had the means of refreshing the air in his chamber at pleasure, by a current of condensed air from the open bell. After some time he desired that they should heave up, which was done; the water-tight cover was unscrewed, and he came out, evidently very much gratified by the success of his first experiment.

He next took his seat in the open bell, and a bell-man took the place he had just ceased to occupy.. The communication between persons descending in this manner, is by writing; they write upon tablets, and mutually exhibit them at the window in the partition. They descended: the bell-man described what he saw to the persons above; and after they had been under water for some time, when Mr. Steele chose to ascend, he intimated his desire to him, and he immediately communicated the order that the bell should be raised. After they came out of the bell, preparations were made for putting the second proposed mode of communication to the test.

An air-tight chamber above water, with a window like the one already described, was connected by a flexible pipe with the open diving-bell; the bell-man took his seat in this, one of the engineer's workmen went into the communicating chamber, and Mr. Steele himself, taking his tablets and pencil, went into the chamber above water, into which he was immediately fastened by an air-tight cover. The bell was lowered under water, and of course the chamber above was filled through the pipe with condensed air.

At this moment a novel and complex system of communicating by conversation and writing, was th: own into action, instead of signals by the strokes of a hammer. Mr. Steele, in the air-chamber above, held conversation with the bellman below, and the man in the communi. cating chamber below, conversed with the persons upon the deck of the vessel. A gentleman stood close to the chamber above, and he and Mr. Steele exhibited writings to each other through the window. The latter wrote, among other things, that he had just asked the man below if he was anxious to be heaved up? and that he had been answered in the negative. The men then made some obser vations about the noise in the bell, caused by the rush of the condensed air through the valve, and about some other circumstances bearing relation to the experi

ment.

At this time, Mr. Steele required some paper; and a sheet tightly rolled was given in to him through a cylinder passing through the side of the chamber.

This was furnished with two cocks, one on the inside, and the other on the outside; so that the paper was transmitted without the escape of the air. Soon after this, I observed that he exhibited at the glass, an order for heaving up; and the bell was raised. When he was liberated, and while he was receiving the congratulations of his friends, I heard him say to one of them, that his feeling was one of extreme delight, at the moment when, looking out from the little window of the air-chamber, after the full success of his experiments, he saw his diving-bell emerging slowly from the water, and the persons who had descended come out from it in safety.

Note by Mr. Steele.

The men in the working-bell under water, are much more comfortable than the person in the air-chamber above, although the condensation of the air be in both cases equal, as the air-chamber becomes very quickly heated and oppressive; and the window looking out upon deck becomes dimmed so rapidly, that it must be frequently cleared, by rubbing it with a handkerchief, I think (but am not at all sure, not having yet proved it by experiment) that I see a practical way of preventing this.

There is an exceedingly interesting, but apparently paradoxical consequence, resulting from the theory upon which the air-chamber has been constructed-1st. Let the diameter of the pipe between this chamber and the bell, be supposed to be increased until it be sufficient to admit a man, and let a rope ladder be inclosed in it. 2nd. Let the air-chamber be subdivided into two, with a man-hole in the partition, and another in the side. It is evident that, by a process analogous to that of passing locks in a canal, and identically the same with that used by Mr. Steele himself, in the transmission of the roll of paper through the two air-tight cocks, a man might go down unwet from deck, to blast docks, or do any other work at the bottom of the sea! The same thing might be effected by the addition of a third compartment to the bell below, between the communicating chamber and the open bell; in which case, the air-chamber above water would (for this particular purpose) cease to be necessary. It is manifest, however, that these two modes of passing and repassing between the deck and the bottom, might be used even in combination.

We perceive from the Notices of applications to Parliament to construet Railways, that the Londoners are likely to be gratified with seeing and possessing one almost in the centre of the metropolis. We allude to the proposed Railway from London to Greenwich. The construction of a Railway through towns has been deemed a task of great difficulty, and to attempt it through so densely peopled a district as the Borough, might be considered almost impracticable. In the present instance, the obstacles in the way are proposed to be got over, by carrying the Railway on a line of connected arches, taking its start and levels from the southern end of the New London Bridge, and terminating opposite Greenwich Park. By this means, no obstructions will be created in crossing the numerous streets, and a splendid bridge of nearly four miles in length, or of a thousand arches, will be exhibited; on the top of which will be laid down the platform for the railway, securely railed in, on which the carriages and passengers will glide in perfect safety between London and Greenwich in less than ten minutes. We shall in a week or two resume this interesting subject more in detail.

INTERIM NOTICES. H. P. L. shall have an early place.

T. R. No. 6, received, and will appear.

Communications received from Mr. Saul-An English Reader-S. Y.-F. H.-An Admirer of English Architecture-Junius Redivivus-Mr. Baddeley-A Constant Reader (Pimlico)-A Lieutenant of Engineers-A Pedestrian-T. J. H.

LONDON: Published by M. SALMON, at the Mechanics' Magazine Office, Wine-Office-court, (between 145 and 146) Fleet Street, where Communications (post paid) are requested to be addressed. Sold by G. G. BENNIS, 55, Rue Neuve, St. Augustin, Paris. GRAY and BOWEN, Boston (U. S.`

M. SALMON, Printer, Fleet Street.