of a body, muft be computed by multiplying the quantity of matter into the velocity with which it moves. Thus, if this new compound of dephlogifticated and æther air expands with ten times greater velocity than any other inflammable explofive air, its force will be about ten times greater. As it feems to be probable, from what is already said, that this compound of explofive air may be put to more ufes than that of an amufing experiment, I think it worth while for men engaged in this branch of natural philofophy 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 difcovery is not far off. The benefit which would arife from fuch a discovery for animal life muft encourage every philofopher to purfue this object. Indeed, if we confider that nitre contains this wonderful aerial fluid in a moft concentrated ftate, and that the nitrous acid feems to be nothing elfe but this beneficial 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 exifts alfo, in a moft concentrated ftate, in bodies almoft every where to be found, as are calces of metal, principally that of iron; that cominon water contains it in 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 elfe 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 inftant when this falubrious aerial fluid will be procured for many useful purposes in a fufficient quantity, either by the difcovery of a ready way to let loofe this air from the bodies in which it is as it were imprisoned, or by filtrating or purifying common air from its impurities? USEFUL USEFUL PROJECTS. Obfervations on Mineral Poifons. O contained an account UR Vol. for the year 1778 of Monf. Navier's propofal of the liver of fulphur as an antidote * against certain metallic poifons. This idea, it appears however, has long before occurred to, and been fuccessfully applied by, others. We have fince feen a paper on this fubject, inferted in the 6th vol. of the Edinburgh Medical Commentaries, wherein alkaline falts are recommended on the fame principle. The directions there laid down are full, clear, and eafy, being drawn up with a view to fupply the omiffion on this head in Tiflot and Buchan, authors on whom the public rely greatly and justly, but who have not noticed this efficacious remedy. As the particular fpecies of poifon taken is often not afcertained, and the women poifoned at Liverpool, in April 1774, with corrofive fublimate, one of whom died, the other, under the direction of Dr. Houlton, took the alkali, by which the found inftant relief, and foon perfectly recovered. The conclufion he draws from the history of this cafe is as follows: In all cafes of poifon it is prudent immediately to give a folution of an alkali, followed by a vomit. If the poifon be 'corrofive fublimate, an alkali, ' either fixed or volatile, will decompofe it, and precipitate the metal in a form nearly inoffenfive. It will have a fimilar effect on the fugar of lead, the extract of lead, emetic tartar, or any metallic falt. If the poifon be arfenic, Newmann ' obferves, that alkalies will very plentifully diffolve it." And if fo, as it is difficultly fo effects produced by it are fo fuddenluble in water, the vomit will on drinking of warm water, &c. "after waiting a while, it will "be proper to give a vomit of ipecacuanha, or, if that is not fufficient, ftill ftronger. "After each vomiting, a dofe of "this folution of falt of tartar "fhould be given, and it may "be repeated every two or three "hours, efpecially if the pain of "the ftomach returns. It thould “be continued too, in small doses, "for fome time after the fymptoms difappear. If none of thefe "falts are at hand, a little wood"afhes mixed with boiling water HE following account of a THE new method of making pot afh was lately read before the Royal Society, and will be inferted in the next publication of that learned body. But as the discovery is highly interefting to the farmer, and the Philofophical Tranfactions are in few hands, I take the liberty of communicating it to the Agriculture Society. I have the honour to be, my lord, your lordship's moft faithful humble Manchester, fervant, April 19, 1780. Tho. PERCIVAL. An Account of a new and cheap Method of preparing Pot-afhes; with Obfervations. HE Agriculture Society at "will answer the fame end, fuf- T Manchefter have long re ་་ TM fering them to fland till they "fettle, and pouring the water commended the making of refer"clear off, or filtering through voirs, for the water which flows from dunghills in farm-yards. This water is ftrongly impregnated with the falts and putrid matter of the dunghill; and by ftagnation it acquires a much higher degree of putrefcency, and probably becomes proportionably more replete with falts. When thus collected and improved, it is pumped into an hogfhead, which being drawn upon a fledge or small cart, is conveyed into the meadows, for the purpose of fprinkling them with this rich manure. This important improvement in rural economy, I apprehend, has not been extended much beyond the diftrict of our fociety; and it feems to be unknown to one of the latest and most intelligent writers on hufbandry. For Lord Kaims, in a recent work on this fubject, of which he has favoured me with a copy, has not even mentioned it. But these reservoirs may be ap plied to a purpofe ftill more fubfervient to public utility, than that above defcribed. Jofiah Birch, Efq. a gentleman who carries on an extenfive manufactory, and bleaches his own yarn, about fix months ago was induced, by a happy turn of thought, to try whether the dunghill water might not be converted into pot-afhes. He accordingly evaporated a large quantity of it, and burnt the refiduum in an oven; the product of which fo perfectly answered his expectations, that he has ever fince continued to prepare these afhes, and to employ them in the procefs of bucking. A ftranger to that narrowness of fpirit, which feeks the concealment of a lucrative difcovery, he is defirous that it should be communicated to the Royal Society, and has furnished me with the following account, together with the plan annexed *. "The 9 cwt. 1 qr. 12 lb. at 42 s. per cwt. "A man and two horfes two days, at 6s. a; 12: 0 120 baskets of coals, at 5d. per basket, "A man's wages for three weeks, "The gain therefore amounts "to 15 4: C, deducting only a trifle for the wear of the pan " and oven." The profits arifing from this preparation of pot-ath, are fufficiently evinced by the foregoing eftimate; and they may, perhaps, admit of increase by future improvements. In the fpring and fummer feafons, I fhould fuppofe, the evaporation might be carried on without the aid of fire; by conveying the dunghill-water from "No. 1. The dunghill. 2: 10:0 £ 19:13: a £4: 9:0 £15: 4:0 the refervoir, through proper fluices, into thallow troughs or ponds, of fuch extent as to afford a fufficient furface for the action of the fun and wind *. These might be covered in rainy weather with awnings of canvas, painted on the outfide black, and white on the infide; the former with a view to abforb, the latter to reflect the rays of light. This pot-afh is of a greyish white appearance, deliquefces a little in moift air, but if kept in a dry room 2. A fough, or drain, round the bottom of the dunghill. near 4. A well to receive the muck water from the pit, wherein a pump "is fixed to convey it to the pan, N° 5, in which it is boiled to the confiftence of treacle, and afterwards burned in an oven. The pan, N° 5, is "formed at the bottom of iron plates; and turned up a little round the edges, to which deal planks are screwed, so as to make it about twenty "inches in depth." The following abridged view of a meteorological regifter, which I kept with great exactness during the years 1774 and 1775, may throw fome light on the practicability of this plan in the climate of Lancashire, which, I believe, is nearly the fame as that of most of the other western counties of England. |