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PREFACE

TO THE FIRST EDITION.

The origin of the following work was a desire to present to students of chemistry an elementary view of the discoveries of Dr. Faraday in Electrical Science. From the very first publication of his Experimental Researches in Electricity, I have felt that from them Chemical Philosophy will date one of its most splendid epochs; and perceiving, at the same time, that the results bear upon them the great impress of natural truths, namely, that they simplify while they extend our views, I have, from the first, availed myself of them in my instruction to my classes. I have enjoyed particular advantages in doing this from the kindness of the discoverer, for in every difficulty which arose, he has assisted me with his explanation and advice. At the same time, when consulted by my pupils upon the best mode of following up the oral instruction of lectures by the study of the subject in books, as they must do who intend to derive benefit from such instruction, I have been greatly at a loss to direct them.

The successive memoirs of an experimental philosopher, who, from time to time, communicates his views as they open out to him during the progress of his discoveries, must necessarily be better adapted to the study of the proficient, than to the instruction of the beginner; and long periods of time often elapse before the facts which they record find their places in general systems.

After some solicitation and much hesitation, I determined to make an effort to supply a want, which, I was perpetually reminded, was urgent, and which did not appear to be likely to be soon supplied from any other quarter.

Upon considering the best mode of carrying this design into execution, I became convinced that the great doctrine of “ Definite Electro-chemical Action," and the laws of “ Electrolysis,” could not be simply and intelligibly stated without a preliminary notice, on the one hand, of the force of local affinity and the laws of definite, multiple, and equivalent proportions in chemical combination; and, on the other hand, of the force of electricity and the laws of electric charge and discharge in matter. A clear description, again, of the action of heterogeneous particles upon each other requires a distinction, which has not been sufficiently attended to, to be drawn between Heterogeneous Adhesion and Chemical Affinity; and it is impossible now to treat of Electricity, without describing the phenomena of its constantlyassociated force Magnetism.

Thus, I was gradually led to include in my plan such a preparatory view of the forces which may be said to

concur to the production of chemical phenomena, as it is absolutely necessary to the student to master, who aspires to comprehend the Philosophy of Chemistry, or anything beyond the mere manual operations of practical chemistry.

It has not been a part of my design to construet a system or manual of chemistry: several excellent works already exist, which render such an undertaking quite unnecessary; but I am not without hope that the following pages may be considered as a fit preparation for the study of such systems.

In executing my task, it has been my aim to lead the student by a more natural method,—that is, more gradually from the known to the unknown—than that which is generally adopted in our elementary books.

In short, if I shall be deemed to have failed in simplifying and facilitating the student's path to the comprehensive science of chemistry, I have failed in the sole object of my undertaking.

In such an elementary work, I have, of course, freely made use of the labours of others, and I regret that my limits have prevented me from mentioning, at all times, the names of those illustrious philosophers, either living or dead, to whom we are indebted for the observation of phenomena, and the fundamental inductions upon which the fabric of science rests. The history of the science of chemistry alone would fill a volume. I have, however,

subjoined a list of those systematic works to whose assistance I have been most indebted.

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I have judged it best in the arrangement of my work, to throw all the graphic illustrations of diagrams, or other figures, into the form of notes; and the explanation and etymology of scientific terms, of words of unfamiliar use, and of words to which it is desirable that the student should attach more definite ideas than are usually suggested by common parlance, I have given in a Glossary. The principal facts and reasoning of the text will thus be uninterrupted by extraneous matter, which, however important as a subsidiary means of explanation, might often confuse the steps of the induction; and those who are acquainted with the terms employed, will not be delayed by definitions which they do not need. It is, however, a caution which cannot be too strongly impressed upon every student, never to pass over a term which he does not understand, without seeking its explanation,

It only remains for me now, to acknowledge my obligations to my friends and colleagues, Professor Wheatstone and Dr. Todd, for their great kindness in undergoing the disagreeable labour of revising and correcting the proof sheets. They have thereby prevented many errors, which would otherwise have deformed the work.

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