u 



PJIEFACE. 



THE progress of modern science, especially 

 within the last few years, has been remarkable for 

 a tendency to simplify the laws of nature, and to 

 unite detached branches by general principles. In 

 some cases identity has been proved where^ there 

 appeared to be nothing in common, as in the 

 electric and magnetic influences ; in others, as 

 that of light and heat, such analogies have been 

 pointed out as to justify the expectation that they 

 will ultimately be referred to the same agent, and, 

 in all there exists such a bond of union, that pro- 

 ficiency cannot be attained in any one without a 

 knowledge of others. 



Although well aware that a far more extensive 

 illustration of these views might have been given, 

 the Author hopes that enough has been done to 

 show the Connection of the Physical Sciences. 



In order to keep pace with the progress of 

 discovery in various branches of the Physical 

 Sciences, this book has been carefully revised. 



076 



