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cattle to be stolen from their rightful owners by a midnight foray * ; in which every man slept with his claymore by his side; and in which the unoffending inhabitants of a retired valley might be murdered in cold blood, because one of their clan had spoken insultingly of a rival chieftain. Such a state of society may be reviewed with enthusiastic interest; but from these retrospective dreams of the mind, we are glad to awaken to the sober realities of less romantic life. In short, we dwell upon these pictures of feudal manners, exactly as we should delight our eyes with the mixture of strength and softness, of grace and wildness. t,' which characterizes the daring paintings of Salvator Rosa. We catch the spirit of his breathing figures. With his predatory banditti we scale the cliffs, and rush down the ravine upon the unwary traveller. But the ardour of imagination would speedily cool, were these reveries of fancy to assume instantaneous existence: we should recoil with horror, were the robbers suddenly to start from the canvass, and did we perceive ourselves to be surrounded by a troop of sanguinary murderers. Art. IV. Chemical Essays, principally relating to the Arts and Manufactures of the British Dominions. By Samuel Parkes, F.L.S. 5 vols. 12mo. price 21. 2s. Baldwin, Cradock, and Joy. London, 1815. THE Author of these Essays is already advantageously
known to the public, by his " Chemical Catechisin," a useful elementary work, which has been well received and has had an extensive sale. He now makes his re-appearance as an author, with the avowed object of diffusing information among that important class of the community, who are engaged in those departments of manufacturing industry that are dependent on chemical principles, and to whom therefore some knowledge of the principles on which their respective arts are founded, is of great and vital importance. For it is an obvious truth, that in proportion as those who are engaged in conducting these processes, shall be conversant with their scientific principles and relations, will be their confidence of always obtaining uniform and successful results ; and their means of introducing such scientific or economical improvements, as may ultimately carry them to perfection.
In the progress of mankind from a state of ignorance and barbarism, to that of refinement and civilization, the arts naturally precede the sciences ; but, during that period, their progress, if indeed they are at all progressive, is extremely slow;
• The Creach.
and the occasional improvement which they may receive, is the result of fortunate accident, and not of well directed inquiry. The establishment of some fixed scientific principles, soon becomes indispensibly necessary to the farther advancement of all which are not strictly manual ; and until these shall have been developed, they must remain circumscribed within the most narrow bounds. Lord Bacon has finely illustrated this subject, by his profound remark, that the discovery of gunpowder was solitary because it was accidental; for had it been the result of scientific investigation, it would have been followed by a crowd of others. This vantage ground being once gained, a new career is opened, which, when compared with the individual capacity of mankind, is of boundless extent. :
We may observe, as a further illustration of this subject, that the periods most strongly marked by great improvement in the arts, will be found to be those which have been most distinguished by the progress of scientific discovery. The discovery and development of the theory of latent heat, by Dr. Black, led in the most direct manner to that great improvement in the construction of the steam engine, which, perhaps more than any other individual circumstance, has contributed to raise the manufacturing establishments of Great Britain to their present unrivalled pitch of greatness.
The “ Essays" which have led to these preliminary observations, are of too miscellaneous' a character, to render them susceptible of very rigorous criticism ; nor do they contain so large a proportion of new matter, as to make it proper to at- . tempt an analysis of each individual essay. They will be found in general to address themselves less to the man of science than to the manufacturer, who, it may be expected, will seek to.." advance his knowledge of the processes about which he is more especially interested, by the most direct and least laborious means. The details are consequently in most instances of a purely practical nature; and Mr. P. has occasionally passed into the description of processes which almost belong to the province of manual arts. This has been especially the case in the essays on glass and earthenware; but though it certainly contributes to make them more generally amusing, yet we doubt if it contributes equally to their usefulness. In general, however, they who wish for information on the subjects of which Mr. Parkes has treated in these volumes, will find them illustrated in a clear and perspicuous manner, and which even those who are not very conversant with scientific chemistry, will not find it difficult to understand. He has indeed shewn great judgement, in keeping the language of his work level with the attainments of those who have never studied chemistry as a
science, but who, from the nature of their occupations, are most likely to be purchasers of bis work, and in whose hands we apprebend it will be found, most extensively useful. His own avocations, and his familiar acquaintance with the science of chemistry, have enabled him to become intunately acquainted with the principles of those subjects on which he treats ; and throughout the work he shews an anxious concern for the improvement of our domestic industry, which proves that the welfare of his country is an object of his constant solicitude. He neglects, therefore, no opportunity of pointing out the relations of the respective arts, with the established principles of chemical science, nor of suggesting inquiries or supplying hints, the investigation of which might lead to considerable improvements.
The successful execution of such a plan as Mr. P. has proposed to himself, requires, indeed, accomplishments which are rarely united in the same individual; a profound acquaintance with chemical science, and an intimate knowledge of those arts which are dependant upon it, not as they are often imperfectly described in books, but as they are really practised in the recesses of our manufacturing establishments. Mr. P. has indeed had many valuable opportunities of acquainting himself intimately with the principles and practice of many of our domestic manufactures, and they have not been thrown away upon him. He has availed himself of them with diligence, and his work may be read with advantage by many, who would be discouraged from seeking information from works which are of a purely scientific character.
There is one feature of this work, which we must not overlook, because it contributes a great deal to relieve the unjformity of more formal details. Mr. Parkes has been very attentive on most subjects, in collecting what may be classed as historical notices, relative to the introduction and progressive establishment and extension of some of the important objects of chemical manufacture; a class of facts which are from their pature very liable to fall into oblivion, but which will merit to be preserved, as contributions to the history of our domestic industry, to which many an ingenious and active individual has essentially contributed, whose name will never find its way to that notice to which it is fairly intitled.
In the selection of the subjects of his Essays, Mr. P. states, that he has chiefly fixed on those which have been least examined by other chemical writers, and 'In all cases due attention has been paid to the improvement of the manufactures of the kingdom. The following are the subjects of the Essays :- On the Utility of Chemistry; on Temperature; Specific Gravity; Calico Printing; Barytes ; Carbon; Sul
Vol. V. N. Š.
phuric Acid, Citric Acid; the fixed Alkalies ; Earthenware and Porcelain ; Glass; Bleaching ; Water; Sal Ammoniac; Edge Tools. The fifth volume consists entirely of Additional Notes and Index.
On perusing this enumeration, it will immediately occur to every chemist, that some of the essays scarcely come within the range of chemical science; and perhaps Mr. P. ought, on that account, to have made the title page of his work more comprehensive and general, for certainly edge tools and specific gravity cannot be regarded as objects of chemistry. Yet those essays will no doubt be found valuable to a certain description of readers; and perhaps that on specific gravity will be the most generally useful of any in the work. We think, however, that the ample space occupied by the first essay, might have been more usefully filled up; for the importance of chemistry, and its extensive application to all the purposes of life, are now so well known, and so correctly appreciated, as to make an essay on such a subject a much less appropriate introduction, than it would have been twenty or thirty years ago.
It is extremely difficult too, on such a subject, to avoid being perfectly trite, and where Mr. Parkes, has endeavoured to give novelty by deviating into less trodden paths, he has unfortunately ventured upon subjects which, being foreign to his pursuits, he does not understand. If there is any class of persons, for example, to whom an exhortation to study chemistry is superfluous, the medical profession is certainly that class, for chemistry forms a constant part of professional education, and it would be grossly incomplete without it. Mr. P. however, in the fulness of his zeal for his favourite science, has recommended it to their sedulous cultivation, for reasons which are less to be admired for their truth than their singularity. After exhorting the medical student, for example, to make himself acquainted with the composition of the different salts, (a very superficial acquirement by the by, for any medical student,) he remarks, This will inspire him with professional confidence; 6 and he will be as sure of producing any particular chemical • effect upon his patient, as he would if he were operating in his own laboratory.' '
This appears to us to be perfect verbiage ; for we have yet to learn, nor does Mr. P. inform us, what resemblance or analogy there can be, between the operation of chemical substances on each other, and their effects on the animal economy. What chemical property of mercury or antimony, for example, will throw the least light upon the power of one in exciting salivation, and of the other in producing vomiting. Mr. P. however, has a remark on the subject, which he may perhaps think will make the matter plain and intelligible, thoug la
we confess it does not do so to us ; nor will it, we apprehend, . to his Readers.
. Besides,' he remarks, the human body is itself a laboratory, in which the varied functions of secretion, absorption, &c. composition and decomposition, are perpetually going on: how, therefore, can he expect to understand animal physiology, so necessary to the practice of physic, if he be unacquainted with the effects which certain causes chemically produce ?'
Time has been, certainly, when, by oxygenating or decarbonizing the blood, or by neutralizing acids or alkalies which were supposed to be present in the fluids, physicians were to accomplish wonders; but these reveries have had their day, and are now as completely exploded as the visions of the alchemists. In fact, whenever men forsake the business of observation for the love of hypothesis, there is no end of human folly and ex. travagance. So far as relates to the arts in general, the importance of chemistry cannot easily be over-rated; but in the practice of medicine it is entirely subordinate, though still eminently useful.
Mr. P. appears to us to place our own country in an una favourable contrast with France, as to the proper appreciation and the facility of acquiring a knowledge of chemistry, to those who are preparing for the active duties of life. But in this we are ready to hope there is some misapprehension, for it is notorious that in Great Britain the means of obtaining an intimate and even profound knowledge of chemistry, are within the reach of every person who, with competent intellectual capacity, has time and money to bestow upon the acquisition.
The vanity of the French character inclines them to make more ļ parade of their institutions than we do ; but we believe our own will be found to embrace every solid requisite for instruction.
It is not our intention to give an analysis of each individual essay contained in these volumes, as such a plan would extend beyond all reasonable limits, nor are they very readily susceptible of being so treated ; we shall therefore offer such observations as have suggested themselves in the course of our perusal, trusting that we shall not be thought uncandid if our remarks should appear to be confined in a great degree to those parts which are most open to animadversion, either from carelessness or inadvertency. In questions of science, accuracy is always highly important, and is generally attainable by the exertion of reasonable diligence; and, in works of science, errors ought therefore not to escape animadversion. Some of these we have noticed in the course of our perusal, and though not numerous, we think it right to point them out. In adverting for example to the advantages arising from a cultivation of chemistry, Mr. P. remarks,