hhh sliding valves for admitting steam from the boiler into the reservoirs, when the cylinders reach the bottom.

ii i conical valves for admitting the steam into the cylinders from the reservoirs, and preventing its escape, when the cylinders begin to ascend.

kk k piston valves for permitting the steam to escape into the dense fluid vessel, when the stems of the valves touch the tops of the vessel, from whence it is drawn off by a pipe communicating with a condenser. These valves are shut again when their stemns come in contact with

777 levers, by which the various valves are opened and closed. oo o projecting springs attached to the interior of the cylinders, and which act upon the valve levers 7, as the cylinders ascend and descend.

This description of the construction of Mr. Williams's engine will render sufficiently apparent its operation. One of the cylinders, when full of steam, will rise with a force equal to the difference between the specific gravity of the cylinder full of steam, and the dense fluid in which it is emersed; and through the instrumentality of the three-throw crank, the cylinders will be successively brought into operation. We fear the patentee has overrated the imperfections of steam-engines of the usual construction, as well as the power to be derived from his own, which, to produce an effect equal to an engine of the common construction of forty or fifty horsepower, would require to be made of a very inconvenient magnitude.

TO THE EDITOR.

London, Nov. 29, 1828. SIR, I beg leave, through your useful publication, to call the attention of miners and the proprietors of coal mines to (what I consider) an improvement upon Sir Humphrey Davy's Safety Lamp, as I feel assured, from some simple experiments, that the wire gauze prevents the flame from passing through it, in consequence of the caloric in its meshes excluding the oxygen of the atmosphere from its support, and not upon Sir Humphrey Davy's theory that the wire gauze cools the flame, or, as he has expressed it, "the cooling powers of solid tissues."

In support of my opinion, I beg to state, that in some of my experiments I found, that when the lamp was cold and newly lighted, and immersed in mixture, that the explosion extended on the outside of the lamp, and that when the lamp was allowed to burn for a few minutes, and immersed in a similar mixture, no explosion took place. I likewise found on throwing a current of hydrogen, or carburetted hydrogen gas, from a bladder and stopcock on the flame of the lamp, that the flame was brought outside of the gauze to the

mouth of the stopcock. In this experiment the mouth of the stopcock must be within half an inch of the wire gauze, and a steady blast continued on the flame so as to cool the intervening wire gauze. When the gauze is as cool as the gas, the flame follows the blast to the mouth of the stopcock. This experiment is supported by one of Sir Humphrey Davy's. See his book on the Safety Lamp, p. 97, where he says, "A small aperture was drilled at the bottom of a wire-gauze lamp in the cylindrical ring which confines the wire gauze-this, though more than one-eighteenth of an inch in diameter, passed the flame, and fired the external atmosphere." AND WHY DID IT DO so? but in consequence of the drilled aperture in the solid brass being colder than the apertures in the wire gauze. My opinion is also supported by what some time since took place at MR. PERKINS's Steam engine Manufactory. One of the tubular boilers partially burst when at a red heat, and the caloric in the rent prevented the water and steam from issuing out until the fire was withdrawn, and the temperature in the rent reduced to the temperature of the water and steam in the boiler.

Paper carbonises on wire gauze over the flame of a candle, but does not inflame. A red-hot coal does not burn or injure a silk handkerchief when the latter is stretched on the back of a watchcase (this experiment is well known), the first cannot inflame from want of oxygen on the under surface, and the other remains uninjured, in consequence of the caloric proceeding from the burning coal producing rarefaction between the coal and the watch-case, and a want of the necessary quantity of oxygen to excite combustion.

It must also be obvious, on a moment's reflection from Sir Humphrey Davy's experiments, that the reason why inflammation cannot be communicated to explosive mixtures in long narrow canals of metal, or in short canals of smaller diameter," is rarefaction produced by the approaching caloric, together with the resistance I shall presently mention, or when confined, and the electric spark applied, that, like gunpowder under pressure, it will be gradually decomposed without explosion. The communication of heat through tubes must depend upon a discovery I recently made in pneumatics, that air is inflicted by the sides of tubes producing resistance inversely as the squares of their diameter, or, in other words, in proportion to the smallness of their diameters, and it is this resistance which contributes along with caloric to the safety of the wire-gauze lamp.

I may also observe, that the experiments of LIBRI, showing that flame is inflicted by metallic rods, and that "when two flames are

"At Cowglen, on the morning of Monday the 10th instant, as George Anderson, Oversman, Gabriel Wingate, Sen., Andrew Bennic, Sen., and James Ross, miners, were proceeding to a distant part of the mine to repair a road, their lamps ignited the gas which had collected at the roof, and an explosion took place, by which they were scorched, the three men slightly, but Mr. Anderson severely. His whole body was one entire blister of a blackish colour. He died on Thursday morning, leaving a wife and nine children to mourn over him."-Greenock Advertiser: copied into the Globe, November 21, 1828.

+ See the Examiner, No. 1076, and Globe, 8072,

made to approach each other there is a mutual repulsion, although their proximity increases the temperature of each instead of diminishing it." Support the principle I advocate, the infliction being occa sioned by the rarefaction of the air between the rod and the flame, the latter seeking for oxygen to support it in a denser medium, the two flames repelling each other for the same reason, and not through any mysterious or "repulsive effect of the wires of the gauze tissue.”*

I have remarked, that whilst the corruscations appear on iron at a white heat (from the decomposition of the air and formation of an oxide on its surface), that it ignites carburetted hydrogen gas, and appears occasionally to attract it, which must arise from the currents and motion produced in the atmosphere by the combustion; whilst, on the contrary, at a red heat it only rarefies the gas, and operates upon it like heat on a fire-balloon making it ascend. These facts prove (which is perfectly reasonable) that the heat which cannot combine with oxygen gas to produce combustion, cannot combine with carburetted hydrogen gas to produce ignition and explosion, and that the wire-gauze lamp requires a shield, that cannot be injured by heat, to make it in reality a safety lamp. The shield prevents a strong current of gas from cooling the wire gauze, and producing explosion, or a weak current from raising the temperature of the wire gauze to a white heat pressing upon it, and producing the same effect; and it is lamentable to reflect on the number of human beings who have perished, and are almost monthly perishing from not using it, and being aware of the causes which contribute to produce perfect safety in explosive atmospheres.

"It being necessary to know the nature of a disease before an effectual remedy can be applied," I have in my improved safety lamp increased the heat to increase the rarefaction, and placed on it a shield of talc to protect the meshes of the wire gauze from being cooled by a current, or exploding at a white heat, an explosive atmosphere pressing upon it. A semicircular shield is sufficient in common circumstances, and to prevent the pressure of air on the gauze consequent on the motion of the miner through the mine; but a circular shield is necessary where much danger is apprehended.

Should the proprietors of coal-mines object to the additional expense in oil and a shield, coal gas may be used with perfect safety, and add to the comforts of the miner by giving him increased light, and (by the arrangement of the lamps in the SHAFT to produce ventilation), an improved atmosphere. The gas-light may be conveyed into the most remote workings, and ascending and descending currents produced in the shaft. The lamp can be lighted without taking off the shield, or gauze covering; by having a close and folding hinge in a segment of the bottom of the lamp, allowing it to open and shut. A little turpentine placed in the cavity of the immoveable part of the bottom, at the mouth of the gas-pipe, and a mixture of nitre and sulphuric acids in an inclined cavity in the moveable part-on the latter being raised up to the ledge to which it is fastened by a spring latch, the mixed acid runs in a groove into the cavity containing the

* See Mechanics' Magazine, Nos. 218 and 259.

turpentine, and an instantaneous light is produced and communicated to the gas on turning the gas-cock, which is on the outside of the lamp.

The person who cleans the lamps should supply the cavities with turpentine (a few drops are sufficient), and the person who has charge of the lighting should supply the acid to prevent the possibility of

accident.

The lamps (after being prepared) could also be lighted or extinguished simultaneously by means of small chains leading to the mouth of the mine attached to a spring lever and index; but this would be more ingenious than useful, and I mention it only to show that I had thought of it, and in connexion with lighting and extinguishing by means of opening and shutting a valve in a box in the bottom of the lamp containing inflammable matter under confinement.

Although there is much difference of opinion among philosophers upon safety lamps, some denying their utility in toto, and others admitting they are useful, while they differ in opinion upon theories, I hope I have said sufficient to convince the most ignorant miner that a shield is necessary, and to induce the proprietors of coal-mines to give the subject their further consideration.

I am, Sir,

Your obedient servant,

RICHARD DILLON.

PLAN AND DESCRIPTION OF A STATIONARY FIRE

ENGINE,

That may be enclosed in an ornamental pillar, and erected at the extremities of the pavements, in front of houses and large establishments.

FIGURE 1 (Plate), is an elevation, and figure 2 a plan of the engine. The letters, in both figures, refer to the same parts. a a, a hollow pillar, enclosing the engine; b, pump cylinder and piston; c, spout; d, circular mouth-piece, to which the hose may be screwed on when wanted; e, a metal plate to separate the spout from the air-chambers; ƒƒ, pavement; gg, valve box under the pavement; hh, water pipe; i, suction pipe, communicating with water pipe; k, suction valve; l, spout valve; m, pump handle; n, an iron fulcrum, resting on the pillar, and may be removed when done with; and, o o, air-chambers, the tops of which, of course, are covered over air-tight.

;

If the area of the pump cylinder in this engine should be equal to the areas of both the pump cylinders in the ordinary double acting fire-engines, and the areas of the spout and air-chambers the same dimensions, the effect would be nearly equal to what is produced by the double acting engines; because there would be as much water forced through the spout valve, by a single stroke of this engine, as there is by a double stroke of one of the others. It may, perhaps,

be worth while to remark here, as I believe it is not generally so understood, that the area of the spout valve "l" ought to be, at least, as large as the area of the piston; because, in the same proportion that it is less, there will be an expenditure of power to no purpose: suppose, for instance, the area of the piston to contain four inches, and, in that case, it would require as much force-as many hands to lift a certain portion of water through a valve of one inch area, as it would to lift four times as much water through a four inch valve.

When the engine is done with, the fulcrum, pump handle, and hose, may be removed to any appointed place that is near at hand ; and the head or cover of the pillar is to be placed upon the top of it; and if the force of the water should be sufficient to raise itself above the head of the pillar, the mouth piece may be closed by a stop cock or valve.

As the suction pipes of these engines communicate immediately either with the main water pipe, or a well, or reservoir, appointed for the purpose, there never can be a deficiency, or a waste, of water, where they are used, as is frequently the case with the other engines, that are obliged to obtain their supplies from water running loose about the streets. Two, four, or half a dozen of these engines in the front of a large house, without being at all in the way, would be an ornament rather than otherwise and would be attended with this advantage, that there would be so many additional engines in full play, at least ten or fifteen minutes before the others could be brought to the spot; and a single engine, at the first breaking out of the fire, might be of more service than a dozen engines some time afterwards. These engines might also be erected in back yards, where the wheel engines could not obtain admission; and if one of them should be erected in the front of every house in a street, there would be at least three additional engines, ready, at a moment's notice, for the protection of each house.

TO THE EDITOR,

SIR, It very frequently happens, on the breaking out of a destructive fire, that there is a complaint of either a deficiency of water, or a delay in bringing up the fire-engines; and it has occurred to me, that both these inconveniences might be in great measure prevented, by the erection of stationary engines, in the form of handsome pillars, in front of houses and large establishments, with suction pipes communicating directly with the main pipes, or reservoirs prepared for that purpose. If you should agree with me, and think that the adoption of the annexed plan might be attended with utility, I shall feel obliged if you will give it a place in your Miscellany, together with any observations of your own that may help to improve it.

July 15.

I am, Sir, &c. &c.

WALTER FORMAN.