the

found in the narrowest parts of rivers, be applicable to inlets of the fee, where the fiream is occafioned by tides? This queftion is answered by M. BRUNINGS in the affirmative; and, as it was proposed with an express reference to that part of the Ye which is to the weftward of Amfterdam, he advifes that the channel fhould be confined by a bank, in order to increase its depth.

The most interefting philofophical Memoir in this volume is one written by Dr. DEIMAN, and M. PAETS VAN TROOSTWYK, of Amfterdam. It was rewarded with a gold medal, as an answer to the following question: What is the nature of thofe different kinds of aeriform fluids, which are feverally denominated fixable, dephlogisticated, inflammable, nitrous, acid, and alkaline air? By what properties is each kind diftinguished from the reft, and from atmospheric air? Have thefe feveral elaftic fluids fo much of the fame nature with atmospheric air, that they may properly be confidered as fo many kinds of air? How far can the nature of the atmosphere be afcertained from experiments and obfervations on thefe feveral elaftic fluids?

The Authors apologize, in their Preface, for their maintain. ing, in this Memoir, an hypothefis different from that fupported in their former Differtation, publifhed in the fifth volume of the Memoirs of the Batavian Society; for an account of which fee, Monthly Review, Vol. Ixvii. p. 512. This circumftance, however, does them honour, as it evinces that truly candid and philofophical spirit which is effentially neceffary to the improvement of science.

They divide their Memoir into three parts, correfponding with the three branches of the queftion. In the firft Part, they give a brief account of the production, both natural and artifi cial, and of the properties of the feveral kinds of air; together with a fummary view of the qualities by which they are diftinguished from each other, and from atmospheric air.

In the fecond Part they endeavour to prove, that all thefe feveral elastic fluids are of the fame nature with atmospheric air, and may thus be confidered as different kinds of air.

In fupport of this opinion, it is here argued, that these elaftic fluids resemble air in every external character; and that the particulars in which they differ, fuch as their degree of acidity, their unfitnefs for refpiration, and their extinguishing fire, are circumftances merely accidental. But, if these permanently elaftic fluids be effentially air, it is natural to enquire whether they are refident in the bodies from which they are produced; or whether they owe their existence to common air lodged in thefe bodies? These queftions are both anfwered in the negative; and it is maintained, that these several kinds of factitious air owe their exiftence entirely to the process by which they are generated. To prove thefe propofitions, our authors enter upon

an investigation, both synthetical and analytical, of the different elaftic fluids, in which they find reafon to adhere to the Stahlian hypothefis, and to reject that of Lavoisier.

In their examination of inflammable air, which appears to be conducted with great accuracy and ingenuity, they combat the opinion of Mr. Kirwan, that it is merely phlogifton; and maintain, that with this a falt is combined, which may be either acid or alkaline; and that the difference between the feveral kinds of inflammable air may be afcribed to the different qualities of the falt employed in their production.

We are forry that the limits of this article will not allow us to enter into the arguments by which our ingenious Authors fupport their opinion. In answer to the objections that are deduced from the experiments of M. la Metherie (who, merely by immerging metals in water, produced inflammable air), they obferve, that this was the cafe only when river water was used, which, if not boiled or diftilled, always contains a confiderable quantity of fixed air. That Dr. Priestley produced inflammable air from iron and zinc, only by heating them, they fay, is no objection to their hypothefis, and they adduce the opinion of Bergman and Scheele, that an acid is a conftituent part of every metal. They deny that inflammable air is a confituent part of water, and maintain that the moisture obferved in the receiver (in which a mixture of inflammable and dephlogifticated air is ignited), is yielded, not only by the decompofition of inflammable air, but in every process by which dephlofticated air is phlogifticated. Befide, from the experiments of Mr. Cavendish, it appears that this moifture is not water, as upon M. Lavoifier's hypothefis might be expected; but an acid, which is dulcified in proportion as it is phlogifticated. To the conclufion drawn by M. Lavoifier, from the production of inflammable air by tranfmitting water through red-hot iron tubes, they object, that this experiment will not fucceed when boiled or diftilled, but only when common water is used to the fixable air contained in this, they afcribe the calcination of the iron, and the production of the inflammable air, which can. in this manner be generated only from zinc and iron; and thefe will yield it without any decompofition of water, only by being exposed to heat.

From their examination of the different kinds of air, our ingenious Authors conclude, that of all thefe, as well as of atmospheric air, acid is an effential part; and that the various characters by which they are feverally diftinguifhed, are owing to the different combinations and modifications of this principle.

Acids, in order to their existence as fuch, feem to require a certain quantity of phlogifton; for in proportion as this is either increafed or diminished, they lofe their acidity; nor can they be APP. Rev. Vol. LXXVII.

made

made to affume the form of air, except by altering their natural proportion of phlogifton. To this the production of the marine acid air may appear to fuggeft an objection: but the process of generating this air is always accompanied with heat, by which the phlogifton contained in an acid is concentrated, one part of it being highly phlogifticated, and the remainder deprived of phlogifton. This effect of heat in phlogisticating one part of an acid at the expence of the other, is apparent in the diftillation of nitre, when a part of the spirit rifes with smoke, and thus feems to be phlogifticated, while the remainder rifes without any colours.

The addition of a fmall quantity of phlogifton will convert an acid into air, which will have all the characters of the acid that conftituted its bafis.

If, befide this additional quantity of phlogifton, an earthy fubftance be combined with an acid, it will become fixable air, in which the characters of acidity will be much weaker, and the original acid not diftinguishable.

The characters of acidity may alfo be diminished by phlogiston alone; for if a larger proportion of this principle be added, the air, thus formed, will fhew lefs figns of acidity; and thefe will become almoft imperceptible when the acid is faturated with phlogifton; in which cafe inflammable air will be generated.

However, in inflammable air there is ftill a character of acidity, which will entirely difappear, if more phlogifton be added, and the acid be fuperfaturated with it; hence phlogisticated air will be produced, in which no figns of acidity can be perceived.

Acids alfo lofe their acidity by being deprived of their phlogiton, and, in this cafe, are converted into dephlogifticated air, in which no character of acidity can be difcerned, unless it be again combined with phlogifton, when it quits the form of air, and returns to a fixed ftate.

What has been obferved of acids in general, may be applied to the nitrous acid in particular. This, however, unites lefs perfectly with phlogifton, and hence, when faturated with it, becomes not inflammable, but nitrous air, which feems to be a medium between acid and inflammable air.

As the nitrous acid is faturated with lefs phlogifton than any other, fo it is more eafily fuperfaturated, and is therefore the moft fit for the production of dephlogisticated air.

That the union of phlogiften with the nitrous, is never fo perfect as with other acids, our authors think evident, from the fmall degree of heat required to make it part with its phlogifton, and from the facility with which nitrous air may be decompofed.

There

Thefe obfervations on the converfion of acids into air, the Authors think, may be extended in fome degree to falts, whether acid or alkaline. From no alkaline falts, except fuch as contain a large proportion of phlogifton, can air be produced; and in this the original falt may eafily be diftinguifhed; but if a greater proportion of phlogifton be added to an alkaline falt, inflammable air is generated, in which the original falt cannot be difcriminated.

In the third Part of their Memoir, the ingenious philofophers examine atmospheric air, which they maintain to be of a nature fimilar to the other kinds of air, like them capable of being united with other fubftances, and of thus undergoing various modifications. They fuppofe it to be compounded of phlogifticated and dephlogifticated air, as its conftituent parts, and are of opinion, that fixable air is only an accidental ingredient, and not effential to it. With regard to its dephlogifticated part, it is difficult to afcertain the acid of which it is compofed; becaufe in every process by which common air can be decompofed, fome acid must be united with it; but from experiments on atmofpheric air dephlogifticated by the calcination of metals, and on the dephlogisticated air produced from vegetables by the heat of the fun, they conjecture it to be the nitrous acid.

Atmospheric, as well as every other kind of air, is found to contain water; but whether this be effential to its existence as air, is not eafy to determine. Yet as we cannot find any acid in a fixed ftate, which is not united with either earthy or aqueous particles, it is probable that water may be infeparable from acids; and this may be the reason that every kind of air produced from them contains a certain quantity of this fluid.

Thus have we endeavoured to give our Readers a general view of the theory maintained in this Differtation, which is fupported by a series of judicious arguments, and well-contrived expe

riments.

The remaining papers in this volume are, an Account of the Cure of a Gangrene of the Scrotum, by Dr. ANDREÆ of Harlingen.-A Relation of the Cafe of a Woman who was completely cured of an Entero Epiplomphalus, in which a confiderable part of the inteftines protruded through a rupture of the abdomen, by B. FRANKEN, Surgeon in Haarlem.-And an Account of a Disorder obferved in the Ifland of Ceylon, refembling the Piica Polonica, by the Rev. JOHN CASPER METZE

LAAR.

M's Vicar

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ART. III.

Relation Abrégée d'un Voyage à la Cime du Mont-Blane, &c. A fhort Narrative of a Journey to the Summit of Mont Blanc. By M. de Sauffure. 8vo. pp. 31. Geneva. 1787.

A

MONG the ftupendous mountains in Savoy, the top of Mont-Blanc was deemed inacceffible, before Dr. Paccard, a phyfician at Chamouni, made the daring attempt to reach its fummit, which, attended only by a single guide, he happily accomplished in August 1786.

M. de Sauffure no fooner became acquainted with the practicability of the journey, than he refolved to undertake it. He arrived at Chamouni, fituated at the foot of the mountain, in the beginning of July 1787, but bad weather prevented him from afcending until the ift of Auguft, when he began his expedition, accompanied by a fervant and eighteen guides, who carried his philofophical and other apparatus. His fon was left at the Priory in Chamouni, and was employed in making meteorological obfervations, with which those made on the top of the mountain might be compared.

Although it is fcarcely fix miles and three quarters, in a ftraight line, from the Priory of Chamouni to the top of MontBlanc, it requires nevertheless eighteen hours to gain the fummit, owing to the bad roads, the windings, and the great perpendicular height of the mountain. That he might be perfectly at liberty to pass the night on what part of the mountain he pleased, he carried a tent with him, and he and his company flept in it, the first night, on that eminence which is firft met with, and which is on the fouth of the Priory, and about a mile perpendicularly above the village.

Hitherto the journey was free from danger, or even difficulty, the road being either rocky, or covered with grafs; but thence, upwards, it was either wholly covered with fnow, or confifted of the most flippery ice.

The fecond day's journey was attended with many difficulties. The ice valley on the fide of the hill must be paffed, in order to gain the foot of that chain of rocks bordering on the perpetual inows which cover Mont-Blanc. The paffage through this valley is extremely dangerous, fince it is interfected with nume rous wide, deep, and irregular chafms, which can only be croffed by means of bridges naturally formed of fnow, and thefe often very flender, extended as it were over an abyfs. One of the guides had almoft perifhed here the evening before, as he, with two others, went to reconnoitre the road. They had the pre

*We have reduced all the French measures to the English standard.

caution