gisticated and æther air fpreads with fuch a velocity through the whole mafs as to be almost instantaneous.

It is well known, that mechanical power chiefly depends upon the velocity with which a body is endowed in the inftant of exerting it; or that the momentum, or force of a body, must be computed by multiplying the quantity of matter into the velocity with which it moves. Thus, if this new compound of dephlogisticated and æther air expands with ten times greater velocity than any other inflammable explosive air, its force will be about ten times greater.

As it seems to be probable, from what is already faid that this compound of explosive air may be put to more uses than that of an amufing experiment, I think it worth while for men engaged in this branch of natural philosophy to look out for a method of producing at pleasure any quantity of dephlogisticated air required. Confidering the rapid progrefs which is daily made on the important fubject of air, I cannot but flatter myself, that this great discovery is not far off. The benefit which would arise from fuch a discovery for animal life must encourage every philofopher to pursue this object. Indeed, if we confider that nitre contains this wonderful aerial fluid in a most concentrated state, and that the nitrous acid seems to be nothing elfe but this beneficial

in

fluid combined with phlogiston, which seems to be imbibed by the vegetable alkali, when the acid is expelled by heat in the form of this air; that this beneficial aerial fluid exists also, in a most concentrated state, in bodies almost every where to be found, as are calces of metal, principally that of iron; that common water contains it great abundance, fo that the light and warmth of the fun extracts it to one fifteenth of the bulk of the water, as Dr. PRIESTLEY found, that even the mafs of our atmosphere is nothing else but this very air foiled with impurities. If we confider, I fay, all this, is it not reasonable to hope, that we are near the important instant when this falubrious aerial fluid will be procured for many useful purposes in a fufficient quantity, either by the discovery of a ready way to let loose this air from the bodies in which it is as it were imprifoned, or by fil-trating or purifying common air from its impurities?

EXPLANATION OF THE FIGURE.

a the pistol barrel.

B the large cylinder or air box.

b the place where the piftol barrel unfcrews from the

air box.

c the pistol handle.

1

, D. the

D the handle fixed to the piston at bb, which is fquare to

prevent the piftons turning round.

E the hole in the fide of the air box.

e the screw to stop the faid hole.

F a piece of brafs with a female fcrew, which was fixed with three strong screws to the wooden handle.

a fcrew at the end of the air box which screwed into

the piece F.

G a piece of ivory fixed to the piston.

K the piston, with the piece of conical ivory fixed to it. L the termination of the ivory cone which filled up the fmall end of the air box.

м the perforation in the wooden handle, through which the brass handle D paffes.

Na brass ball at the end of a wire, which paffes down the canal R in the ivory cone.

o another piece of wire paffing down the other canal, canals are filled with non-conducting fubftance. P an interstice between the two wires of about one line, through which the electrical spark, when given on the ball N, paffes and fets fire to the inflammable air in the air box.