ΤΟ

MICHAEL FARADAY, D.C.L., F.R.S.,

FULLERIAN professor oF CHEMISTRY IN THE ROYAL INSTITUTION,

&c. &c. &c.

MY DEAR FARADAY,

To you I dedicate this attempt to place amongst the elements of science the great discoveries with which you have adorned this prolific age. I know that you will not be displeased that I have thought them capable of being made the subject of familiar teaching.

The success of even this humble effort, should I not fail in my purpose, will be owing to you; for to your kind encouragement and ever ready explanations I owe the facilities which I have enjoyed in following you closely in your splendid career.

I must, however, be careful not to make you responsible for too much. You know that the consequence of repeating all your experiments has been that I have myself been led to experiment; and it may be that I have incorporated with your views speculations of my own of by no means so just a nature. My unaffected conviction is, that, in what I may differ from you, mine will be found to be the error, while yours must be the chief credit in what we may agree.

But whatever you may think of my philosophy, I have the happiness to feel assured that you will not lightly regard the sentiment of sincere affection with which I subscribe myself,

MY DEAR FARADAY,

Your faithful Friend,

J. FREDERIC DANIELL.

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