X PREFACE TO FIRST EDITION. 



will be seen to have relation to the progress and 

 actual state of the physical sciences. Written with 

 the object of such illustration, they will, I trust, be 

 read under the same view ; that is, not as formal 

 treatises on these several subjects, but as general out- 

 lines, denoting the new methods and spirit of modern 

 research ; the more recent and remarkable discoveries 

 in each science ; and those mutual connections of all, the 

 knowledge of which is among the highest attainments 

 of man in his study of the natural world around him. 



In these Articles, more purely scientific, many alter- 

 ations have been required ; partly from the rapid 

 growth of physical knowledge since they were first 

 published; partly from the collected form in which they 

 now appear. Various additions have been made, either 

 in the text or by notes, to remedy deficiencies from the 

 former cause ; many omissions also, to obviate the 

 repetitions which could scarcely be avoided in papers 

 written at different times, and for different Eeviews. 

 To meet the same requirements, I have further, in seve- 

 ral cases, transferred portions of one article to another ; 

 or even taken parts from essays not included in this 

 volume. A few anachronisms will probably still be 

 found ; but none such, I trust, as can create error or 

 embarrassment to the reader. Certain repetitions also 

 may be noticed (as with regard to the influence of 

 the Atomic doctrine on Modern Chemistry) ; but these 

 will be seen to depend on the particular object of the 

 first Essay, which, treating of physical science, at large, 

 necessarily took its illustrations from the several branches 

 of science composing this great whole. 



