oxyds formed with the four simple combustibles, those of sulphur and phosphorus are at the distance of many hundred pages from those of carbon and hydrogen; and muriatic-acid, being a simple substance, is insulated from all the rest of the acids. These instances certainly detract something from the excellency of the present work; yet we think that such defects bear no proportion to the real merits of this elaborate performance. 03691-950 We concluded the former part of our critique with the Simple Substances; we now proceed to the Compound. These Dr. T. has divided into Primary, or such as are composed of two simple substances; and Secondary, or such as are formed of two compound bodies. The Primary Compounds are arranged under, 1. Alkalies; 2. Earths; 3. Oxyds; 4. Acids; 5. Compound Combustibles. Fifty-seven Primary Compounds are here enumerated; and much valuable information may be derived from this part of the work. Twelve of these, viz. the fixed, alkalies (though earths) and the fluoric acid, having never yet been decomposed, ought, consistently with the author's plan, to have been placed among the simple substances.

Dr. Thomson divides Acids into, 1. Products of Combustion; 2. Supporters of Combustion; 3. Combustible. Lavoisier's opinion, that oxygen is universally the acidifying principle in acids, is proved to be erroneous; since some bodies (sulphurated hydrogen, for instance) have all the properties of acids, and yet contain no oxygen, while many other bodies possess oxygen, without any of the characteristic properties of acids. An account of Compound Combustibles, under which are comprehended, Fixed and Volatile Oils, Alcohol, Ethers and Tan, finishes the subject of Primary Compounds. 220dq

The Secondary Compounds are, 1. Combinations of Earths; 2. Glass; 3. Salts; 4. Hydrosulphurets; and, 5. Soaps. We have already observed, that the science of Chemistry is greatly indebted to Dr. T. for his very judicious arrangement of the vast variety of Salts. When it is considered, that upwards of 600 of earthy, alkaline, and metallic salts have been already formed, the chemical student might be almost in despair of arriving at the knowledge of their different properties; yet, by Dr. T.'s classification of these salts, it is no very difficult task to learn what is yet known of them. His principal ingenuity is exerted on the metallic salts, as being the least known. Besides giving appropriate names (which seem to correspond very well with the prevailing Chemical Nomenclature) to such Metallic Salts as have but one acid and one base, differing only in two portions of oxygen; he has divided every genus into five heads, corresponding with their different properties: viz. 1. Detonating; 2. Incombustible; 3. Combustible; 4. Metallic; 5. Triple. This distribution, however, is only attended to so far as these salts have

been

been pretty fully investigated; and its principal advantage, at present, seems to consist in pointing out an eligible method, by which the investigation of future chemists may be regulated on this important branch of the science. In the concluding section an Salts, Dr. T. makes some pertinent remarks on salts in general, and endeavours to draw the attention of his readers to the investigation of this difficult subject, by pointing out the great importance of salts in chemical analysis.

'But it is not,' says he, strictly true, that many of the salts are altogether useless. It may be affirmed, with the greatest truth, that, even at present, there is not one among them, the knowledge of whose properties is not of some advantage. One of the most important and difficult things in Chemistry, is to ascertain exactly the nature and composition of different bodies. Now this can only be done by observing the changes produced upon them by other bodies, and the compounds which they are capable of forming. Thus, if, on examining a substance, I find that, when combined with sulphuric acid, it forms a heavy insoluble white powder; with muriatic acid, a very soluble salt, which crystallizes in tables, and is insoluble in alcohol; with phosphoric and oxalic acid, likewise an insoluble powder, &c. I conclude, without hesitation, that it is barytes, &c. &c. Thus it is the knowledge of the salts, which the different alkalies, earths, metals, and acids, are capable of forming, which enables us to discover their presence when they enter as ingredients into different compounds. Here then is a reason for studying the properties of the salts, independent of their utility as individual bodies; and it may be affirmed with truth, that chemical skill is in every case proportional to the extent of their knowledge.' Vol. iii. pp. 120, 121.

Having copiously treated the subjects of Salts and Hydrosulphurets, Dr. T. proceeds to the different kinds of soaps, viz. Alkaline, Earthy, and Metallic. This Chapter we consider as very defective. In speaking of the soap made with wool, as a substitute for oil, no explanation whatever is given of the principle on which this substitution succeeds, nor any information afforded beyond the simple fact. Dr. T. also mentions the fact of hard soap being made from potass, by means of a large portion of the muriat of soda, as a mere chemical experiment, which has answered the purpose with tolerable success; whereas we believe that this is the general, if not the only mode of forming it in our largest manufactories on this side the Tweed. The reader also, who wishes to be informed on what principle it is that acts as a detergent, or why carbonat of potass or soda would not answer the purpose equally well, without the mixture of oils, will consult Dr. T. on this subject in vain. The author does, indeed, too often content himself with stating facts, without mentioning the principles from which they result. Half a line, or a mere reference to a preceding part of his work, would frequently have been quite sufficient for the whole explanation,

soap

We

We now proceed to the third book, which is devoted to the very important doctrine of Affinity; a doctrine which lies at the foundation of Chemistry, and is that to this science which gravitation is to Natural Philosophy. It is on this account that we conceive Dr. T. ought to have commenced his work by discussing this subject. He has divided it into four› Chapters. Chap. I. treats of Affinity in general; II. Of Homogeneous Affinity; II. Of Heterogeneous Affinity; IV. Of Repulsion. With respect to the apparently great variety of laws, to which the doctrine of affinities is subject in relation to different bodies, Dr. T. contends, with much ingenuity, that they are reducible to one general law, modified, indeed, by particular circumstances, but fixed and invariable, like that of gravitation. The different intenseness of affinity towards different bodies, he con ceives may be owing principally to the different distances be tween the particles of such bodies as have affinities for one another, and that the peculiar figures of these particles may be the cause of this difference in their distances. Upon the whole, he comes to this very proper and modest conclusion;

It is certainly possible, therefore, that attraction, both sensible and insensible, may not only vary at the same rate, and according to the same laws, but be absolutely the same force inherent in the atoms of matter, modified merely by the number and situation of the attracting atoms. This is certainly possible; and it must be allowed that it corresponds well with those notions of the simplicity of nature in which we are accustomed to indulge ourselves. But the truth is, we are by no means good judges of the simplicity of nature; we have but an imperfect glimpse here and there through the veil with which her operations are covered; and from the few points which we see, we are constantly forming conjectures concerning the whole of the machinery by which these operations are carried on. Superior beings smile at our theories, as we smile at the reasonings of an infant; and were the veil which conceals the machine from our view, to be suddenly withdrawn, we ourselves, in all probability, would be equally astonished and confounded at the wide difference between our theories and conjectures, and the real powers by which the machinery of the universe is moved. Let us not, therefore, be too precipitate in drawing general conclusions; but let us rather wait with patience till future discoveries enable us to adyance farther; and satisfy ourselves in the mean time with arranging those laws of affinity which have been ascertained, without deciding whether it be the same force with gravitation, or a different one.' Vol. iii. p. 188.

We cannot pass over the ingenious manner in which Dr. T. has discussed the difficult subjects of Attraction and Repulsion, without remarking, that the author possesses a mind capable of great abstraction, and qualified to investigate subjects of the most subtle nature. His ideas are clear, his illustrations pertinent, and he has a great facility in rendering abstruse subjects

compa

comparatively easy and intelligible. Matter for two or three ex cellent introductory chapters to Dr. T.'s course of chemistry might be collected from his Treatise on Affinity, Saturation, Neutralization, Repulsion, &c. reserving the more minute and philosophical investigation of these subjects for the place which he has allotted them. This, we think, would be of great service to the chemical student, and seems, indeed, absolutely necessary to enable him to enter with advantage on the study of chemical. analysis.

We have now arrived at the second grand division of this; work; the Application of Chemical Principles to the Solution of the Phenomena of Nature, or what Dr. T. entitles, a "Chemical. Examination of Nature." Under this head are discussed, the Atmosphere, Meteorology, Waters, Minerals, Vegetables, and Animals. It would far exceed our limits, to enter into a detail of the vast variety of interesting matter contained under each of these particulars. It must suffice to say, that throughout the whole the author has manifested his usual ability, and furnished the student of this science with abundance of interesting infor mation; and though we certainly cannot accord with all his ingenious speculations, (for the subject affords infinite scope for speculation), yet we think that Dr. T. has done more toward the illustration of these difficult parts of philosophy, than has been performed by any former writer.

We shall lay before our readers a short extract from this part of the work, on account of its general importance. It relates to the means of destroying contagion, and is the result of Morveau's experiments on this subject. He exposed air infected by putrid bodies to the action of various substances; and he judged of the result by the effect which these bodies had in destroying the fetid smell of the air. The following is the issue of his experi

ments.

1. Odorous bodies, such as benzoin, aromatic plants, &c. have no effect whatever. 2. Neither have the solutions of myrrh, benzoin, &c. in alcohol, though agitated in infected air. 3. Pyrolignous acid is equally inert. 4. Gunpowder, when fired in infected air, displaces a portion of it; but what remains still retains its fetid odour. 5. Sulphuric acid has no effect; sulphurous acid weakens the odour, but does not destroy it. 6. Vinegar diminishes the odour, but its action is slow and incomplete. 7. Acetic acid acts instantly, and destroys the odour of infected air completely. 8. The fumes of nitric acid, first employed by Dr. Carmichael Smith, are equally efficacious. 9. Muriatic acid gas, first pointed out as a proper agent by Morveau himself, is equally effectual. 10. But the most powerful agent is oxy-muriatic acid gas, first proposed by Mr. Cruickshanks, and now employed with the greatest success in the British Navy and Military Hospitals. Thus there are four substances which have the property of destroying contagious matter, and of purifying the air; but acetic acid cannot easily be attained

in sufficient quantity, and in a state of sufficient concentration, to be employed with advantage. Nitric acid is attended with inconvenience, because it is almost always contaminated with nitrous gas. Muriatic acid and oxy-muriatic acid are not attended with these inconveniencies; the last deserves the preference, because it acts with greater energy and rapidity. All that is necessary is to mix together two parts of common salt with one part of the black oxide of manganese, to place the mixture in an open vessel in the infected chamber, and to pour upon it two parts of sulphuric acid. The fumes of oxy-muriatic acid are immediately exhaled, fill the chamber, and destroy the contagion.' Vol. iii. pp. 333,

334.

It will be seen, from the account which we have given of this System of Chemistry, what our opinion is of its merits. Though we have pointed out a few of its defects, yet we consider the whole as comprising the most numerous facts, selected with the greatest judgement, and digested on the whole in the most convenient form, of any work on Chemistry extant. Though professedly a Compilation, as indeed every work of this nature must chiefly be, yet it abounds with experiments, well conceived and executed, by the author himself; and his name will be handed down to posterity among the most illustrious chemical philosophers. It is printed in a remarkably neat and correct manner; and, considering the quantity of letter-press, the work is very cheap. We could have wished to see a few more plates illustrative of chemical apparatus; because many will study Dr. T.'s System of Chemistry, who have no opportunity of attending a regular course of Lectures, or of viewing the different apparatus necessary for experiments; and it is desirable, that, in a work in most other respects so complete, they should have every thing that is necessary for studying it with success.

Art. XI. The Crisis; or, the Progress of Revolutionary Principles. A Poem. By William Peebles, D. D. 8vo. pp. 200. Price 6s. 6d. Bell, Edinburgh; Vernor and Hood, London.** 1804.

DURING the late threats of invasion, it may be doubted,

whether, to the everlasting honour of the British Muses, there was a harp left unstrung in the cause of its country. Whether the very humblest rhymester, tuning his reed in the poet's corner of a newspaper, did not exert himself, again and again, in the cause of King and Constitution-in recruiting the volunteers of his neighbourhood-in animating, like another Tyrtæus, the shepherd and the ploughman to the fight-and in painting our friend and well-wisher, Buonaparte, even blacker than he is, or than humanity can possibly be. Every monthly, weekly, and daily publication teemed with poetry, or with loyalty and heroism at least. Last summer, too, we remember a very useful periodical pamphlet, the ANTIGALLICAN, which, collected into

volumes