« PreviousContinue »
rity; that is, to have particular attracting points or surfaces, whose attraction is counterbalanced by a certain quantity of latent heat, and which rush together when that heat is sufficiently diminished. Whatever tends to bring the particles into a state more advantageous to their junction, as by presenting their attracting surfaces more directly to one another, forcing them nearer together, removing contrary attractions, &c. must baften the congelation : thus a piece of ice, having its attracting surfaces already in the most favourable position, and their power probably stronger from their union, promotes the attraclion of the particles of the still 'Auid water. He pursues these speculations at some length, and concludes them with another rather more unexpected in an experimental enquiry.
• It seems most probable (he says) that the particles of matter in general are nothing more than centres to certain attractive and repulfive powers; on which hypothesis it may be understood, that if two or more of these central points are brought much within the limits of their respective attractions and repullions, these powers will no longer be equal at equai distances from their common centre. Now fuch a combination of central points may be considered as one particle of any particular matter; and the unequal distances from the common centre at which the attractions and repulsions are equal, will define what may be called the shape of that particle. And if, at equal distances, the attraction or repulsion is much greater at one point than at another, that will constitute a polarity.' An Account of Experiments made by Mr. John M Nab, at Albany
Fort, Hudson's Bay, relative to the freezing of Nitrous and Vitriolic
Nitrous. particulars were deduced from reasoning, in a
Freezing manner which did not ftrike the generality of Strength. readers with much conviction. The present 568
-45 experiments were made to ascertain the truth
-30 of it; and their results agree, for the most part, 508 -18 sufficiently well with the former, except in a
9 few inftances where fome deception had pro
4 bably happened with respect to the strengths of the acids.
4 The freezing points, corresponding to the
-10 different ftrengths, are now determined, from
-18 the whole, as in the annexed table; where the
298 --28 mark means below o, and + above O, on
Vitriolic. Fabrenheit's scale. The strengths are exprefled by the weight of marble which 1000 parts of
-26 the acid are capable of diffolving or farurating.
918 This is a very good way of trying, as well as
+42 expreffing, the strength of nitrous acid; but in 758 - 45 * See Monthly Review, vol. Ixxvi. p. 192. Y 3
478 448 418 388 358 328
trying the vitriolic by this method, an uncertainty would arife, on account of the selenite formed in the operation, which somewhat defends the marble from the further action of the acid. The strength of this acid was therefore computed from the weight of plumbum vitriolatum, formed by the addition of sugar of lead : a quantity of oil of vitriol, fufficient to produce 100 parts of that compound, was found adequate to the saturation of 33 parts of marble; that is, to saturate as much fixed alcali as a quantity of nitrous acid does that would diffolve 33 of marble.
Specific gravity would perhaps have been a better criterion, and would likewire have enabled us to compare these experiments with Mr. Keir's *; which cannot now be done without very troublesome and delicate experimental investigations, except in one inftance, where Mr. Cavendile has himself determined the gravity of his acid. He informs us, that the gravity of 1,780, the ftrength at which Mr. Keir found oil of vitriol to freeze moft easily, answers to his strength of 848, which is very near to the last but one in the above table: the freezing points also correspond very nearly, Mr. Keir's being +46, and Mr. Ca. vendith's +42 Experiments and Obfervations relating to the Principle of Acidity,
the Compofition of Water, and Phlogifton. By Joseph Priestley, LL.D.F.R.S.
That water is composed of two kinds of air, vital and inflammable, is almost universally admitted as one of the moft important, and beft ascertained discoveries of modern chemiftry. “How is it possible (says M. Lavoisier, with his associates +) to doubt of it, when we see that by burning together 15 grains of infiammable air and 85 of vital air, we obtain exactly 100 grains of water; and that, by the decomposition of water, we recover the fame principles, in the same proportions? If we could doubt of a truth established on experiments fo fimple, fo palpable, we should no longer have any thing certain in phyfics ; we ought equally to question whether vitriolated tartar be really composed of vitriolic acid and fixt alcali, fal ammoniac of marine acid and volatile alcali, &c. &c. for the proofs which we have of the composition of these falis are of the very same kind, and not at all more rigorous than those which establish the composition of water.” When Messrs. Baumé, Cadet, Darcet, and Sage ,
* See M. Rev. for March last, p. 184.
+ Lavoisier, Bertholet, and Fourcroy; in their report, to the Academy, of Haffenfratz and Adee's new system of chemical characters, June 27, 1787.
I In' their report of the New Chemical Nomenclature, June 23, 7787. See Rev. for July laft, p. 74.
ftated to the French Academy their doubts respecting this doctrine, observing that an immenfe quantity of heat and light is disengaged in the combustion, and that the water might have been held in solution by.chis beat, as it is in the atmosphere; the above correspondence in weight was urged as a decisive proof against them, for when 100 grains of the two airs produce exactly 100 grains of water, it is impollable that all this water could have previously exifted in the airs.
It appears, however, after all, from the paper now before us, that this correspondence of weight, on which so much stress has been laid, and which makes the basis of the whole doctrine of the composition and decomposition of water, has actually no existence. Nor, perhaps, is ic fo surprising that inaccuracies and deceptions should happen in experiments of so much delicacy, as that a theory so important should be raised, with so much confidence, on a foundation so apparently deceitful, and fo insufficiently explored,
By repeating, in a more accurate manner, the experiment of the combustion of the two airs, with due precautions to previoully separate from them as much as possible all extraneous moisture, Dr. Priestley has now found, that the weight of the water produced falls always far fhort of the weight of air decomposed; and, instead of air being a component part of water, he has made ic probable that water is a component part of air.
It is already known that inflammable air cannot be produced without water; and the Doctor shews, by several experiments, that the case is the same with respect to fixed air: the aerated terra ponderosa, wbich appears to have no water in its compofition, yields no fixed ajr till water is introduced ; and 43 or 44 grains of the water are always expended in the production of 100 grains of air ; so that, of this air, water makes near one half, It is probable, that the same thing obrains in every other kind of air, fince water is employed in the production of them all; that pure water is their proper bafis, or the fubitance without wbich no aeriform fluid can sublist; and therefore that water has never been either composed or decomposed in any of our operations.
The water, produced by the combustion of the two airs, was always found to contain an acid. The experiment was often repeared, and on a large scale, in order to procure suficient quan: rities of the water for the necessary trials; and a rigorous examination of it, by Mr. Keir and Dr. Withering, thewed clearly that the acid is the nitrous. This also is an important discovery; for phlogisticated air has hitherto been thought neceffary to the formation of nitrous acid.
Doctor Priestley obierves, that the doctrine of the decomposition of water being set aside, that of phlogijlon (which, in consequence of
the late experiments on water, has been almoft universally abandoned) will much better ftand its ground, as all the newly dircovered facts are more easily explained by the help of it,' and indeed we do not see how they can be explained at all without it. He confiders, for instance, the inflammable air obtained from fulphur and metals by passing steam of water over them in a red hear. If this air does not proceed from a decomposition of the fteam, it muft receive its principle of inflammability from the sulphur or metal, which therefore cannot be simple bodies, as the antiphlogistic theory makes them to be. This inflammable subftance cannot be supposed to be real sulphur, or real metal, becaufe, whatever body it be obtained from, it is found always to poffers the same properties, to be transferable to other bodies by the same laws of affinity, and to produce with them the same compounds.
In our preceding account of this volume (See our last month's Review, page 249 ) we noticed the meteorological journals, on which the following remark has occurred to us, fince the article was printed, viz. That two observations in the day seem too few for collecting the mean heat of the twenty-four hours; especially when they are made at ftated hours, which hours (7 A. M. and 2 P. M.) are in some seasons of the year nearly the coldest and hottest in the twenty-four, but in other seasons, neither the one nor the other. From our own observations, which have been extensive, and often repeated, at short intervals, during the night as well as the day, the greateit cold (excepting in extraordinary circumstances) appears to be, in all seasons, about fun-rise, and the greatest heat about the middle of the interval between noon and sun-fet: but we do not pretend that a medium between these two would be the true mean heat of the 24 hours. To ascertain that, the continuance of the respective degrees of heat ought to be taken into the account.
Art. IX. A fort and plain Exposition of the Old Testament, with des
votional and practical Reflections, for the Use of Families. By the Rev. Job Orton, S. T. P. Published from the Author's MS$. ' by Robert Gentleman. Vol. I. * 8vo. 68. Boards. . Longman, &c. 1783. R. Job Orton was a Diffenting Minister, of considerable
reputation, at Shrewsbury. Several of his publications have been commended in our Review. It appears from the pre
• This work is now printing by subscription. The proposals inform us, that it is hoped the whole will be comprised in five volumes 8vo. but will not exceed fix; that a head of the Author will be engraved; and that an account of his life will be given with the latt volume.'
face to this work, that for more than twenty years he made the expounding of the Scriptures a conftant part of his public services. As he apprehended that a short and plain exposition of the Old Testament, with practical reflections at the end of the chapters, was much wanted for the use of families, he (toward the close of his life) put the papers, which he had formerly written for the pulpit, into the hands of the Rev. Mr. Palmer of Hackney ; 'earnestly requesting him to prepare them for the press. In an advertisement prefixed to this volume, Mr. Palmer says, “Having such other engagements as rendered it impossible for me to proceed in this great work with fuch dispatch as to finish it in any reasonable time, I at length determined to resign it, with all my material:, into the hands of my worthy friend Mr. Gentleman *, who, on various accounts, appeared to me the ficceft perfon I knew to execute the design of the worthy projector.'
Mr. Gentleman, in the preface which follows, gives an account of the manner in which he has proceeded in executing what he conceived to have been the Author's defign. He candidly confesses, that had the work received the finishing hand of the Author, or been published under his own inspection, it would no doubt have been more complete. This we can easily believe; but we think that the generality of plain Christians, who have not so much relish for learned criticisms as for devotional and practical reflections, may find it an agreeable and use ful family-book, and as such we recommend it.
• A Diffenting Minister at Kidderminster, Worcestershire.
ART. X. Military Antiquities respekting a History of the English Army,
from the Conquest to the present Time. By Francis Grose, Esq. F. A. S. 4to. 2 Vols. 41. 45. Boards. Hooper. 1988.
E announced to the Public, in our Review for Sept.
1786, p. 203. that Captain Grose had published five Numbers of the Military Antiquities; and we then laid before our Readers the proposed objects which the Author had in view. The work is now completed, and its contents will appear from the following account.
Although the history commences with the Norman invasion, yet, in order to elucidate bis subject, the Author previously gives a brief description of the military establishment of the AngloSaxons, previous to the sime of that event.
Personal attendance in war, for the defence of the country, being a branch of the Saxon's trinoda neceffitas, obliged every freeman, capable of bearing arms, and not incapacitated by bodily infirmity, in case of a foreign invasion, internal insurreátion,