PREFACE. THE best apology that can be offered for presenting this volume to public notice, will be found in the reason which suggested its compilation, viz., the absence of any system of physics, sufficiently extended to include all those subjects. with which men of education, especially members of a liberal and important profession like that of medicine, ought, and are required, to be familiar with; and at the same time not too diffuse to disgust or weary the student. To the student of medicine, and chemistry in particular, the want of a concise and yet sufficiently comprehensive work on physics has been long felt; as, without an acquaintance with the physical sciences, his professional education must be considered as far from complete; and, independently of this, a knowledge of the principles of these sciences has long been rendered imperative at the different medical boards, and has constituted an important part of the examination which the candidate for a diploma is called upon to undergo. The following manual is chiefly intended as a text-book for the student whilst attending lectures on physics, or as preparatory to his entering upon the study of larger, and more elaborate works. With this view it has been written; and as the great difficulty experienced in executing this task has arisen from the necessity of knowing, not what to insert, but what to omit, whenever a doubt has arisen on this point, it has been determined by a reference to the amount of knowledge required of the student, by the different English and Scottish medical boards. A work of this kind I had long ago projected, in consequence of not being acquainted with any in the English language, to which I could refer the students attending the lectures on physics, annually delivered at Guy's Hospital; although I had hitherto shrunk from the task, hoping that a production, so much required by the medical and general student, would have emanated from some writer. more able As an apology for the arrangement followed in this volume, it must be observed that utility and extreme simplicity, rather than elegance of style, were sought for, and every other object has been sacrificed to obtain this end. The division into numbered paragraphs was adopted, as every chapter would thus become a kind of running commentary on the others, and would, moreover, facilitate reference to distinct subjects in the Analytic Index. I regret, as every writer on so extensive a series of subjects must do, the impossibility of doing justice to every labourer in the field of philosophic enquiry, by referring each discovery to its author: as far as this could without circumlocution be effected, it has been done. For discoveries of longer date, as they have become the common property of science, there needs no apology for not in every case mentioning the name of their authors in a strictly elementary work. I have been greatly indebted to several writers in the French and German languages, for many suggestions and illustrations, of which I have never hesitated to avail myself whenever they appeared to divest any subject of obscurity, or to add to its interest. To the "Précis de Physique" of Biot, the "Eléments de Physique" of Pouillet, the "Traité de Physique" of Hauy, the "Positions de Physique" of Quetelet, and the "Grundriss der Experimental-Physik" of Kastner, I have been peculiarly indebted for several illustrations, some of which have not, I believe, previously appeared in an English dress. Having thus explained the object and unpretending character of this volume, I trust enough has been said to blunt the edge of criticism, should such, perchance, be levelled against it. The critic himself, I would beg to remind of the celebrated observation of Horace "Sunt delicta quibus non ignovisse velimus, Nam neque chorda sonum reddit quam vult manus et mens; Those readers who desire further information on the subjects treated of in this work, and have not the assistance derived from attendance on lectures, may, if only a popular acquaintance with them be required, refer to the very elegant, although as yet unfinished, "Elements of Physics" of Dr. Arnott, or to Sir David Brewster's edition of "Euler's Letters to a German Princess." Those who require a more profound acquaintance with these important subjects, should consult the books referred to in the body of this volume, as well as to the treatises published by the Society for the Diffusion of Useful Knowledge. The series of Essays written by the professors of King's College, London, now in the course of publication, will also furnish most valuable comments on this, and other elementary works. In the execution of this task, I have experienced but one source of regret, and one which every person engaged in the duties of a laborious profession must feel, when called upon to write on a series of subjects, to a certain extent distinct from his immediate duties, and requiring for their elucidation a much greater amount of time, than his more onerous engagements will allow him to devote to them;—this source of regret arises from the feeling, that a work of this kind had not appeared from the pen of one better fitted to the task, than of him who now offers it to public notice. Wilmington Square; October, 1839. |