and there it lodges until it is forced into the thoroughfares of the mines, in the way before described.

Various are the descriptions of longwork, and also the mode of commencing it, but the above will show the advantage of working the coal by long-work over the stall and pillar system. The coal is all taken away, and not left in the earth, in such shameful quantities as Mr. Ryan and Mr. Buddle represent it to be in the Northern Collieries. Neither need coal be left at all, if worked by the stall and pillar system; the pillars may all be taken out, and are done so daily (in all the collieries, at least that I am acquainted with.)

From this, I hope, Mr. Ryan will see the possibility of ventilating a coal mine by what he calls the diluting system; and, also, how it happens, that more dreadful explosions take place in the Northern Collieries than in any other in this kingdom. In Shropshire, of late years, the ventilation of the mines has been so perfect, that we seldom hear of any accidents by fire-damp. There is some trouble at times in opening a new colliery in that district; but when a communication is once effected from pit to pit, all trouble with hydrogen gas is over; although even in that coal field it is a very active agent.

I agree with Humanitas in every thing he says in favour of the working collier. I am sure that a more useful set of men exists not in the kingdom; and I only wish their toils, dangers, and hardships, could be better rewarded.

66 WONDERFUL DISCOVERY IN MECHANICS."

[We extract this article from the Baltimore American; but rather for the amusement than the edification of our mechanical readers. The new moving power, described in such extravagant terins, seems to be of that numerous class, in which the machine is absurdly supposed to contain a power within itself independent of every external force. The gravity with which the only difficulty in the case that of steering clear of ships propelled by any of the ordinary means -is highly amusing. After all, the “

new

power" is only to accomplish a passage across the Atlantic in 15 or 18 days; and that has been done repeatedly by sailing vessels.-ED. M. M.]

"I went to the Exchange Readingrooms to look at the Wonderful Lever, which filled me with the greatest admi. ration. I have, therefore, thought it a duty to the public to publish my observations on it. This lever, or to speak more correctly, the two watch-barrel screw-levers placed in a wheel, with water buckets, presents really to the eyes of the scientific observer one of the most wonderful discoveries, power and velocity united, that ever excited the wonder of man, combining the utmost simplicity with its other excellence, and owing nothing to gas, compression of air or steam, the power of which it infinitely surpasses. It consists of two very broad and flat watch-barrels, with a large hole in the middle, and two screw levers to each of the barrels, one within and one without. The inner one is fixed at its centre to a long and wide petre in the barrel hole, fixed by a point within, and enters another little petre, both free. The shaft passes through the small tube, and is solid, fixed by its basis ou the wheel. This is the fulcrum. The other end of the lever-screw is attached to the end within the barrel; the other placed on the cover of the barrel, is fixed at the end on the border of the barrel, and the end of the centre has a square hole in which the shaft passes at the other end of the barrel. The watch barrels are placed one at each end within the wheel. In the middle there is a large and broad hoop attached by two triangular levers, one opposite the other; the end of the short branch of the lever and the two other branches, are fixed on by their fulcrum to the edge of the wheel. The whole apparatus occupies less than two feet of span in the wheel, and is, as it were, suspended upon principal points in the centre of the wheel, or carries its power there. The opinion of the best informed persons is, that this invention will, by its great advantages and economy, prove a certain and rapid growth in navigation. In fact, a vessel will cost three times less in building. A vessel of any size can sail on the open seas without any other aid than the lever. One wheel placed within the vessel is enough. A power sufficient to keep up the motion of the wheel is enough. The greatest power is in the wheel, and this force is equal to 100-horse power. A voyage to Europe will be completed in 15 or 18 days, without any risk, except that of coming in contact

PROPOSAL FOR AN ENLARGED APPLICATION OF TIDAL POWER.

66 6 Τα εν ποσι."

Sir, I have prefixed to this paper, the motto, "Ta ev Toσi," which, as you know, is part of the sentiment of an ancient Greek, who used to marvel at the strange conduct of the speculatists of this day, in directing their investigations in the pursuit of knowledge and profit to the extremities of heaven and earth, while they neglected the means and advantages at their feet. Nature, in her quiet, and every-day life, constantly offers to us inexhaustible magazines of disposable power; but in vain; for we seem not to value her gifts unless we extort them from her by violence and torture. You will, I suppose, Sir, perceive, that I am thinking of the exclusive and indiscriminating ardour with which the powers developed by fire are cultivated, to the neglect of those mighty forces which nature offers spontaneously.Among those which ought most immediately to strike us islanders, are the tidal forces.

We see, every day, on our coasts, a boundless stratum of water, elevated several feet, and depressed as many every six hours: what a magazine of force is there! It is only necessary to cut off a part of it, to constrain it within limits, and the leviathan is straightway at our service, a patient and indomitable drudge. This has been partially done by the contrivance of tide wheels; but these, at best, are but bad economisers of the irresistible power that moves them; they cannot move effectively more than six hours out of each twelve, and are, for so long, little better than undershot wheels. 1 beg to propose the following hint, as not unworthy discussion in your work.

If a space be enclosed on the sea beech with water-tight walls, and covered with an air-tight flat roof, so that

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the lowest high water-mark may be level with the roof, we have here a magazine of force, powerful according to the di imensions of the space enclosed.

I am nothing of an engineer; so that with very great diffidence, I submit the following rough calculation; principally, indeed, to set the wits of your contributors at work on the subject.

If the space enclosed be 1000 feet square, if the tide rise six feet at the lowest neap, and if there be flood gates so adapted, as to fill the enclosure in just six hours at all tides: if this arrangement be effected, water will enter, or tend to enter, at the rate of 1,000,000 cubic feet per hour, and produce an equivalent pressure on the air, within, say, of 70,000,000 lbs. per hour. If now an engine, similar to a steam-engine, be connected with the enclosure by a tube, and work off the air at the same rate, at which the water enters, it will be served with power at the above rate, equal, I believe, to the consumption of the largest steam-engines.

This will last, however, but for five hours; for, as the engine cannot be set to work till after the tide has risen one hour, so it is high water without, when the last foot of air comes to be worked off. As this foot would supply only a continually decreasing power, it ought to be blown off by a valve, so as to allow, the water to fill the enclosure up to the roof. The valve then being closed, and another hour allowed to elapse, the air may be worked into the enclosure, with the same effect with which it was worked out; requiring only, it may be, a separate working cylinder, as the pressure will now be atmospheric, instead of hydrostatic, as before. Here, again, when it comes to low water, the last hour should be allowed to run off by the admission of air through the same valve. The whole performance then will be at the rate of 70,000,000 lbs. per hour, for 20 hours out of the 24.

I hope, Sir, this idea may be thought worthy of pursuit by your contributors; for I should like much either to see it proved visionary, or developed into praetical utility. A magnificent vision rises before my imagination, as I conceive the merchants of a wealthy manufacturing seaport combining and constructing such an enclosure of a mile square, and dividing among themselves for the purposes

more than the whole of the sum originally calculated; but it is to be observed, that the work is longer, larger, and much more massive, than was at first intended. It appears that the late Mr. Ralph Dodd's driftway had actually proceeded 1040 feet,

377

in 1808, before the irruption, which put a stop to the plan. We fear that its gigantic successor will have scarcely a better fate, although it is a pity that it should be abandoned, after so much has been done. F. H.

are commonly used in locomotive machines. This is only part of an im provement (with a little alteration) which I mean to bring forward in the condensing engine, as soon as I can have the whole proved by model.

Before describing these drawings, it may be as well to state my objections to the valve commonly used in locomotive engines, being that termed the short slide. It is a fact, well known to practical engineers, that by this valve a column of steam equal to the capacity of the nozzle pipe (measuring each branch, from the face of the valve to the inside of the cylinder port) is wasted at each revolution of the crank shaft; which I take to be a matter of importance.— Again; from the steam escaping at the same part by which it enters the cylinder, the eduction must remain the same as the steamway; which, I fear, is another loss of power in high pressure engines. Regard must also be had to the water produced by condensation in the cylinder, and the connected tube. For example: I shall suppose myself in the act of raising the steam, with the throttle valve shut; but not altogether steamtight, which seldom is the case now; the steam pipe from that valve to the boiler, being exposed to the action of the external air, a portion of water is generated in it, which, along with what may be in the steam chest, nozzle pipes, &c., must enter the cylinder in advance of the steam; this with what may be generated in the cylinder, must be ejected by force (on the return of the piston) through the nozzle pipes to the eduction port, although the nozzle pipes (with the space allowed for clearance between the piston and cylinder covers) still remain full, and it passes again into the cylinder by the action of the steam upon the water; this water (of course) being of a much lower temperature, it is evident, that condensation commences immediately on their meeting, and continues throughout the workings of the machine; affording a proof, I may almost call it an ocular proof, that horizontal and diagonal cylinders with these valves, are never free (while in operation) from a column of water on each side of the piston; which, I fear, is more destructive to power than has hitherto been calculated on. I shall now attempt a description of my inven tion, which, I trust, will be understood,"

and go far in removing the objections: above stated.

Fig. 1st.-Is a transverse section of the cylinder, cut off so as to show the steam and eduction ports. A A is the cylinder, and BB a metallic ring, ground steamtight into a recess made in the cylinder for its reception, as better shown at a and b (Fig. 2nd.); the ports are cut through the cylinder and ring (Fig. 1st.) where six are exhibited on the steamway side, and seven on the eduction side of the cylinder; the space marked C and E in both figures passes round the cylinder, (as shown by the dotted lines in Fig. 2) for the reception of steam, which I will term the steam chest; it is divided in two by the bars marked c c (Fig. 1st.) which rise to meet the covers, and are made steamtight there to prevent any communication between the steamway and eduction,

Fig. 2nd. Is a longitudinal section of the cylinder with what may be termed the bottom cover. The steam is admitted at A (on the upper side of the cylinder, where the throttle valve may be placed) passing along B into the steam-chest C, from whence it enters the cylinder D, by the parts a, as is more plainly shown in Fig. 1st. Having performed its duty,

the metallic ring is made to shift, and the steam, with any water that may be in the cylinder, is permitted to escape by the ports b (on the under side) into the chest E, and thence by Finto the open air at G. By this simple arrangement, it will be seen that no steam can be wasted, and a clear cylinder is procured for a fresh supply every stroke.

The metallic rings may be made double, as shown in the drawings (after the manner of some metallic piston rings) or they may be in one with a slight de- ..{ gree of bevel, and kept steamtight by screws tapped in the cover. The covers may be fitted nearly close to the rings, with openings cut opposite each port to the curve of the dotted lines, or they may be rounded off in that form. The ports can be so constructed, that the rings will not require to shift more than 14 inch, and from a considerable portion of their surface never having to pass the ports, they ought to continue good for a length of time. T. RONTREE.

Yours, &c. 6, Canning street, Liverpool, 1 Jan, 4, 1832.