more perfect manner than has been heretofore accomplished; their process is described as follows:

"After the oil has been removed from the cloth, it is to be dried. A composition is then made of rye flour and pure water, in the proportion of four quarts of the flour to eight gallons of water, which is to be boiled to the consistency of a thin paste, or the flour may be mixed in hot water.The cloth is then to be made sufficiently wet with the paste (which may be applied either warm or cold,) and put into the same kind of fulling mills, and beat about, as is customary when soap or steam is used. When the cloth has been sufficiently fulled in this manner, the paste is to be washed out or scoured with pure water.

"In the same manner a thin paste, made of wheat oats or barley flour, may be employed, and other vegetable substances of a similar nature may be used in the process of fulling with great advantage: the employment of vegetable matters, instead of animal matter, in the process of fulling, being the substance of the invention.

"By using these materials, the cloth becomes fulled to a proper thickness in a much shorter time than with soap; is softer, firmer, and less worn in the mill; costs (in America) one-fifth the expense of fulling with soap, and retains the colour of indigo blues, and all other colours that are dyed before fulling, in greater perfection than when soap Is employed."

IDEA OF AN AIR ENGINE.

SIR.-I have long entertained an idea, that an engine might be so contrived, that it could be worked by a succession of powerful explosions of condensed air through a valve, on the principle of the air-gun; but I have given the subject more attention since steam engines were applied to propel vessels at sea, and since the distressing accidents that have occurred by the use of fire. In the ardent hope, however, that the following (I admit) crude suggestion may meet the eye, and attract the attention, of some person qualified to entertain the subject, I shall proceed to detail my ideas.

On the mere supposition that a

3

force is required equal to the power of steam, to rapidly raise the lever of the engine, I propose that immediately under the piston of an engine there should be placed a large cylinder, capable of containing a sufficient quantity of condensed atmospheric air; over the valve of which cylinder the piston should closely enter to a proper depth, and be ready, on the action of a spring or trigger, to receive the whole force of the explosion, and thus violently force up the lever in the same proportion of power as is now done by steam. With a view to check the sudden shock the engine would thus receive, an arm spring of sufficient power might be applied to command the piston inside, and at the top of the cylinder. Another explosion from the chamber of condensed air would bring down the piston with equal force. With the view to keep this chamber (containing the condensed air) constantly charged to the very highest pressure, whereby an equally effective discharge could be made each moment, I propose that an air-pump should be attached to the engine, which could be worked by the common motion of the lever ; or that a man should turn a wheel, which, by being connected with other wheels, springs, and proper machinery, the valve of the air-cylinder would be opened, and the air therein brought to act against the extremity of the piston, which would thus be forced up with extreme violence, thus raising the lever; in a second of time, the air pump could then force in as much as had escaped in the first discharge or explosion, and then, in equal and due time, the piston would be ready to receive a second explosion, of precisely the same power as the former, to bring it down. Thns, by a well-regulated and scientific movement, in rapid succession of powerful discharges of condensed atmospheric air. a force could be brought to act up and down fully equal to steam.

As the air-pumps would be by this constant work rendered very hot, which would heat the cylinder or airchamber so much, that thereby the air might be dangerously rarefied, I propose that the pumps should be

encircled or enclosed in a case with a sufficient quantity of cold water, and which, by a simple contrivance, in a certain number of turnings of the wheel (equal to five minutes' time,) could be let off, and a fresh supply of cold water made to rush in from a reservoir above, to supply the place of the water heated by the barrel and

tion worthy of a page or two in your useful Magazine, you will greatly oblige me by inserting it.

I have the honour to be, Sir, your most obedient servant, W.H.C.

water, so often repeated, or made to be constantly running off, would serve to condense the air in the cylinder, and enable it to receive a greater quantity than it otherwise would.

If it should be considered that one cylinder would be insufficient to force the piston up, and then down, there might be two cylinders, one to force it up, and the other to force it down; and if so, then the air-pump could be filling the one during the expulsion of a part of the air in the other; thus both would be kept alternately working. Each chamber might be capable of containing, upon the principle of the air-gun, as much air as would hold fifty discharges; one only of which discharges would be let off against the piston, on which the airpump would instantly after force in a fresh supply of air to the very highest pressure: thus every discharge would be of equal force. The man who turns the wheel could have his movements regulated by a given scale, or pendulum; and it is not improbable that, in places where the engine could be placed in a fixed and steady position, the whole machinery could be worked (provided the air-chamber was previously charged) by a powerful clock and multiplied wheel movement, with heavy weights and maintaining power, which could be wound up every twenty-four hours; or after the attendant had left off the first explosion, the machinery could be so arranged, that, by the turning of a wheel, every succeeding explosion could be let off by the action of the engine itself on the trigger attached to the cylinder.

It is almost needless to observe, that if something like this plan could be carried into effect, the great expense of fuel would be saved, and safety ensured from fire.

If you, Sir, shall think this sugges

COAL TO PREVENT THE CORRUPTION OF WATER; BY A. CHEVALLIER.

Having been consulted by M. B. on the means of preventing the water of a pond in his garden from becoming offensive, I suggested the use of Animal Charcoal, and begged him to let me know the result of the experiment. A letter addressed to me on

the 15th of November last assures me that the experiment has succeeded perfectly. The following is an extract of the letter:

"There is a pond, of nine feet in diameter and three feet deep, in the garden of M. B., the water of which is used for watering the garden. The pond is filled with water from a well; but, on the approach of autumn, it becomes offensive, and a mephitic odour arises from it.

"When it was annually cleaned out (an operation for which buckets were found necessary,) there was found in the bottom a putrid slime, which rendered this work very disagreeable, and perhaps dangerous.

"This year, on the 10th August, 1823, M. B. had 45 lbs. of animal charcoal, in powder, thrown into the pond; being careful to have it spread equally, by means of a basket of open wicker-work carried over the surface of the water: the powder which floated was soon precipitated to the bottom.

"This water was used for watering, and partly renewed as it became necessary. The waterings ceased about the middle of September. The water, which was then 20 inches deep, was left undisturbed, and has not been since changed; and although it is discoloured and even greenish, it is entirely inodorous-thanks to the animal charcoal.”

M. B. Having sent me a bottle of the water, I observed, on examining it, that it had neither a disagreeable smell nor taste; and that, during the eight days which have elapsed since its removal from its carbonaceous bed,