feet in a fecond; that the elaftic force of the fluid generated from this powder, at the inftant of its production, was only 307 times greater than the mean elaftic force of common air: whereas, according to Mr. Robins's theory, the elaftic force of the fluid generated from gunpowder is 1000 times greater than the mean preffure of the atmosphere; fo that the force of aurum fulminans (we should add, in this mode of trial) appears to be to that of gunpowder, as 307 is to 1000, or as 4 to 13 very. nearly.

Though, from fome late experiments, it appears, that this fingular powder actually generates, when ignited, four times the quantity of elastic fluid that is produced by an equal bulk of gunpowder t; we are not surprised at the comparative inferiority of its force, as exhibited in the Author's experiment. The nitre, and confequently the immenfe bulk of dephlogisticated air contained in gunpowder, enable that compound to burn and explode in veffels perfectly clofe: but this is not the case with aurum fulminans, which, expofed to the strongest heat, in a ftout veffel which is perfectly closed, is reduced without noise or explosion. That it exploded therefore at all in the Author's trial, is to be afcribed only to its having been imperfectly confined: though, on the other hand, that very confinement prevented its exploding with fuch violence, as when it is ignited in the open air.

The Author made feveral attempts to increase the force of gunpowder, by the admixture of various fubftances. He firft endeavoured to combine the explofive power of gunpowder with the well known explofive force of water and other fluids, when reduced to the ftate of an elaftic vapour. He accordingly introduced into the middle of the charge fome air bladders of small fishes, in each of which was included a small portion of water: but the force of the charge, inftead of being greatly increased, as might be expected, from the converfion of the water into an elaftic fream, was fenfibly diminished.

It is not perhaps difficult, after the event, to account for the Author's failure in this experiment: for granting even that the flame of the gunpowder was fufficiently intenfe, and of fufficiently long duration, to convert all the water into an elastic vapour; it is to be obferved that this vapour is not permanently elaftic, unless the fides of the veffel which contains it are heated to the fame degree that is neceffary to the production of the elastic vapour.

No better fuccefs, and probably for the fame reason, attended the Author's trials with fpirit of wine, and mercury; which

+ See the ad volume of Bergman's Opufcula Phyfica 5 Chemica, lately published, p. 162.

laft

laft requires a very extraordinary degree of heat to bring it into, and maintain it in, the state of an elaftic vapour. The Author had apparently better grounds to expect fuccefs, on adding 20. grains of falt of tartar to 145 grains of gunpowder; as he thus conftituted a kind of pulvis fulminans: but the force of the powder was very fenfibly leflened by this addition; as it was likewife in fome fubfequent experiments, when he mixed fal ammoniac and brafs duft with the gunpowder.

The laft attempt of the Author's was that of fhooting flame inftead of bullets.' Having often obferved paper to come out of great guns and small arms inflamed; he was led to try whether inflammable bodies, and particularly fluids, might not be ignited, and projected from fire-arms, fo as to communicate the fire to other bodies at a confiderable diftance. On trial, however, he found that he could never fet dry tow on fire at the distance of five yards from the muzzle of the barrel. He repeatedly dif charged large wads of tow and paper, thoroughly foaked in the moft inflammable fluids, fuch as alcohol, etherial spirit of turpentine, balfam of fulphur, &c.; but none of them were ever fet on fire by the explofion. He fometimes difcharged three or four. fpoonfuls of the inflammable fluid, by interpofing a very thin wad of cork over the powder, and another over the fluid. The fluid did not take fire, but was projected against the wall, and left a mark where it hit. If the experiment had fucceeded,' adds the Author, it would have turned out one of the most important discoveries in the art of war that have been made fince the invention of gunpowder.'-We rather rejoice that the Author did not fucceed in this difcovery; which would not only have made an addition to the horrors of war, already too numerous; but might poffibly be applied to many mischievous and dreadful purposes in civil life.

Article 26. Further Experiments on Cold, made at the Macfarlane Obfervatory belonging to Glasgow College: By Patrick Wilson, M. A. &c.

Thefe experiments are a continuation of fome fimilar trials made the preceding year; and of which we gave an account in our Number for April 1781, pag. 275: but they cannot be here properly abridged. One fact, however, merits particular notice; we mean, the power of ardent fpirits of diffolving fnow, and thereby producing a very powerful freezing mixture.

A certain quantity of alcahol and of fnow, which were each at 8 degrees below the freezing point, or at + 24o, being suddenly and intimately mixed, the temperature became, in the fpace of 20 feconds, no less than -28° i. e. 28 degrees below o of Fahrenheit's thermometer. This is a cold only 12 degrees fhort of that which Fahrenheit first produced by ufing fpirit of nitre for the experiment.-There was employed only

about

about a pint of alcohol; but the proportion of fnow was not attended to.'

Article 29. A farther Account of the Ufefulness of washing the Stems of Trees: By Mr. Robert Marfham, of Stratton,

F.R. S.

This fubject was treated of by the Author in the 67th vo lume of thefe Tranfactions. In the present article he shews, that the benefit of cleaning the stems of beeches and other trees continues feveral years.

Article 31. Experiments on the Power that Animals, when placed in certain Circumftances, poffefs of producing Cold: By Adair Crawford, M. D.

The refrigerating power which living animals poffefs, is afcribed by the Author partly to the increased evaporation, and to the diminution of that power by which the blood in the natural ftate is impregnated with phlogifton;' and, in part, to the conftant reflux of the heated fluids towards the internal parts. The experiments on frogs, &c. here related by the Author, and his reasonings upon them, cannot conveniently be abridged. Article laft. An Account of fome Thermometrical Experiments, &c. relating to the Cold produced by the Evaporation of various Fluids ; -the Expanfion of Mercury-and a Defcription of a Thermometrical Barometer: By Tiberius Cavallo, F. R. S. &c.

The most curious part of this Article is the defcription of the Author's peculiar method of producing an extraordinary degree of cold by the evaporation of fluids, and particularly of ether. By this method, even when the atmosphere was hotter than temperate, he has brought the mercury in the thermometer as low as 3 degrees above o F. or 29 degrees below the freezing point. In the fame manner, in any season of the year, he converts a fmall quantity of water, contained in a thin glass tube, into a folid and hard cylinder of ice. In bringing the mercury in the thermometer down to +3°, he obferves that, if the ether be very good, or capable of diffolving elastic gum, and the thermometer have a small bulb; not above 20 drops of ether are required to produce this effect, in about two minutes; but that nearly the fame effect may be produced by employing only the common ether in a greater quantity, and for a longer time.

The greatness of thefe effects is principally to be afcribed to the smallness of the stream of ether, which is made to iffue from the capillary aperture of a tube, which is connected with the vial that contains that fluid. In former experiments of this kind, a great part of the cold that had been generated was loft, by dipping the thermometer or other veffel into the body of the comparatively warmer fluid.

The Author gives an account of an easy and singular method of purifying Vitriolic Ether, communicated to him by Mr. Winch.

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Winch. To a given quantity of common ether, double the quantity of water is to be added; the liquors are to be agitated, and after refting three or four minutes, the water is to be fuffered to run out through the mouth of the inverted bottle. More water is then to be added, and the fame operation is to be repeated three or four times. The ether, which is now left fwimming on the furface of the water, is faid to be exceedingly pure: fo that ether, which could not affect elaftic gum, now very readily diffolves that fubftance; and appears to the Author to be purer than any that he has ever met with, that has been made after the beft ufual method, and in the most careful manner. The operation is not however of the œconomical kind; as not above three or four ounces remain after this purification of a pound of common ether. The Author does not inform us, whether these remaining three or four ounces can be any further diminished by agitation in water; or whether this purified ether is hereby rendered no longer foluble in that fluid. Should this be the cafe, the procefs is fo far curious, as well as ufeful; as it indicates an actual decompofition, in fome degree, of this finguJar fluid. The water in which the ether has been wafhed fhould therefore be particularly examined, in order to detect that principle to which the common ether owes its folubility in water.

We fhould not omit to obferve, however, that the abovementioned results are very different from thofe mentioned by fome of the lateft inquirers into this fubject. Mefirs. Baumé, Macquer, and others, affirm, that water diffolves about a tenth part of its bulk of ether; and that, on the other hand, the ether diffolves a certain portion of the water, fo as to become more weak and aqueous. We can scarce conceive, that the mere quicknefs with which the ablution is here faid to be performed can produce fo confiderable a difference in the refults.

In the remaining part of this Article the Author inveftigates the expanfion of quickfilver by different degrees of heat; and propofes the conftruction of a thermometrical apparatus, which, by means of boiling water, fhall indicate the height of the barometer to within one-tenth of an inch; fo as to be commodioufly employed in the room of the common portable barometer, in measuring the heights of mountains, &c.

MISCELLANEOUS PAPERS. Article 18. On the Heat of the Water in the Gulph Stream: By Charles Blagden, M. D. &c.

The Gulph fream is a conftant and rapid torrent, which fets along the coaft of North America, to the Northward and Eaftward; and which is croffed by all fhips going from Europe to any of the fouthern provinces of North America. The water of this ftream is feveral degrees hotter than that of the fea into which it ruas. The Author defcribes and explains the advanREV. Aug. 1782.

K

tages

tages which feamen may derive from the ufe of the thermome ter; by means of which, they may accurately afcertain the time when a fhip enters that ftream, and its diftance from the coaft, &c.

Article 22. Some Calculation of the Number of Accidents or Deaths which happen in confequence of Parturition, &c.;_ taken from the Midwifery Reports of the Wefiminfer General Dispensary, &c. By Robert Bland, M. D.

In this Article the Author defcribes his method of keeping the register of the midwifery patients in the hofpital; from which he has formed-a table of natural, difficult, and fatal labours; a table of the proportion of male to female children, of the number of twins, and of the children that were deficient or monitious, and of thofe that were dead born;-a table of the ages at which women begin and ceafe to be capable of bearing children;-tables of the number of children born by 1380 women together with a table of the chance of life from infancy to 26 years of age, &c.

-Art. 21.

It will be fufficient to give the titles only of the remaining Articles. These are-Article 16. Account of a luminous Appearance in the Heavens; by M. Tiberius Cavallo, F. R. S. Art. 17. Account of an Earthquake at Hafodunos near Denbigh; by John Lloyd, Efq; F. R.S.-Art. 19. Account of the Appearance of the Soil, at opening a Well at Hanby in Lincolnshire; by Sir Henry C. Englefield, Bart. F. R. and A. S.. Abstract of a Regifler of the Barometer, Thermometer, and Rain, at Lyndon, in Rutland, 1780; by Thomas Barker, Efq.-Art. 23. Account of a Child who had the Small Pox in the Womb; by William Wright, M. D. F. R.S.Art. 24. Natural Hiftory of the Infect which produces the Gum Lacca; by Mr. James Kerr, of Patna Art. 25. Account of a Phenomenon obferved upon the Iland of Sumatra; by William Marfden, Efq.and Art. 28. An A count of the Ophidium barbatum Linnei; by P. M. Auguftus Brouflonet, M. D.

The Mathematical and Aftronomical Papers are referved for a future Number of the Review.

ART. VIII. A Vindication of the Political Principles of Mr. Locke: in Anfwer to the Objections of the Rev. Dr. Tucker, Dean of Glocester. By Jofeph Towers, LL. D. 8vo. zs. fewed. Και Einfon. 1782.

Tis no very pleafing tafk as we ourselves have often experienced-to follow fuch a Writer as Dean Tucker through all the doublings of fophiftry and mifreprefentation. Yet, where thefe unfair weapons are employed to wound an established and eminent character, or to attack the fundamental principles of

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