

AUTHOR'S PREFACE. 



HAVING undertaken to prepare a course of Lectures on natural philo- 

 sophy, to be delivered in the theatre of the Royal Institution, I thought 

 that the plan of the institution required something more than a mere com- 

 pilation from the elementary works at present existing ; and that it was 

 my duty to collect from original authors, to examine with attention, and 

 to digest into one system, every thing relating to the principles of the me- 

 chanical sciences, that could tend to the improvement of the arts subser- 

 vient to the conveniences of life. I found also, in delivering the lectures, 

 that it was most eligible to commit to writing, as nearly as possible, the 

 whole that was required to be said on each subject ; and that, even when 

 ;an experiment was to be performed, it was best to describe that experiment.! 

 1 uninterruptedly, and to repeat the explanation during its exhibition.' 

 Hence it became necessary that the written lectures should be as clearly 

 and copiously expressed, and in a language as much adapted to the com- 

 prehension of a mixed audience, as the nature of the investigations would 

 allow ; and that each experiment, which was to be performed, should also 

 be minutely described in them. If, therefore, there was any novelty either 

 in the matter or the arrangement of the lectures, as they were delivered 

 for two successive years, it is obvious that they must have possessed an 

 equal claim to the attention of a reader, had they been published as a 

 book ; and upon resigning the situation of Professor of Natural Philosophy, 

 I immediately began to prepare them for publication. 



I had in some measure pledged myself^ in the printed syllabus of the 

 lectures, to make a catalogue of the best works already published on the 

 several subjects ; with references to such passages as appeared to be most 

 important : it was therefore necessary > as well for this purpose, as in order 

 to procure all possible information that could tend to the improvement 

 of the work, to look over a select library of books entirely with this 

 view, making notes of the principal subjects discussed in them, and exa- 

 mining carefully such parts as appeared to deserve more than ordinary 

 attention. Hence arose a catalogue of references ; respecting which it is 

 sufficient to say, that the labour of arranging about twenty thousand, 

 articles in a systematic form, was by no means less considerable than that 

 of collecting them. The transactions of scientific societies, and the best 

 and latest periodical publications, which have so much multiplied the 

 number of the sources of information, constituted no small part W the 

 collection, which was thus to be reduced into one body of science. 



