PREFACE. 



Having undertaken to prepare a course of lectures on natural 

 philosophy, to be delivered in the theatre of the Ro3'.al Institution, I 

 thought that the plan of the Institution required something more than 

 a mere compilation from the elementary works at present existing; and 

 that it was my duty to collect from oi'iginal authors, to examine with 

 attention, and to digest into one system, every thing relating to the 

 principles of the mechanical sciences, that could tend to the improve- . 

 ment of the arts subservient to the conveniences of life. I found also, 

 in delivering the lectures, that it was most eligible to conmiit to writ- 

 ing, 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 uninterruptedly, and to repeat 

 the explanation during its exhibition. Hence it became necessary th^t 

 the Avritten lectures should be as clearly and copiously expressed, and 

 in a language as much adapted to the comprehension of a mixed audi- 

 ence, as the nature of the investigations would allow ; and that each 

 experiment, which was to be performed, should also be minutely de- 

 scribed in them. If therefore there was any novelty either in the mat- 

 ter 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 pubUcation. 



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 



