Entered, according to Act of Congress, in the year 1839, by HARPER & BROTHERS, In the Clerk's Office of the Southern District of New-York. PREFACE. X In undertaking, at the request of the publishers, to select from a number of English works one which would serve as an introduction to natural philosophy, suited to the purposes of the School District Library, great difficulty was experienced in the choice. Of the books submitted by them, some were too difficult to be understood, while those of a more popular character were deficient in scientific accuracy, or behind the present state of knowledge. While thus engaged, an "Introduction to the Study of Chymical Philosophy," by Professor Daniell, of London, came, by the politeness of its author, into the hands of the editor. On perusal, it appeared, although intended for a far different purpose, to contain matter in the very form and of the very description which was wanted. While, therefore, an apology may seem due to that learned gentleman for stripping his work of the very parts which constitute its direct object, the editor feels satisfied that he is presenting to the American public the most lucid composition of the leading facts and principles of natural philosophy which has yet appeared in the English language. In adapting the work of Professor Daniell to the present object, all that was strictly chymical has been omitted, and with it the exposition of the views of Faraday in relation to the connexion of electricity with chymical affinity. Some few alterations have been made in the text to adapt it to the American reader, and a variety of additions have been introduced to render the work more general and popular in its character. The most considerable of these have reference to magnetic and optical instruments, and to acoustics. Columbia College, Oct., 1839. J. R. |