PREFACE. XV 



knowledge of the same agent, as it operates 

 in all the phenomena of nature, would aug- 

 ment the resources of happiness a thousand 

 fold dispel the clouds of error which have so 

 long hovered over the sciences, and enlarge 

 the empire of man over the material world, 

 in an endless variety of ways. It is animating 

 to think how soon this grand result might be 

 brought about, if all the talents now wasted on 

 fruitless speculations were rightly employed 

 in the study of nature. 



It may be right to inform the Reader that a 

 brief outline of the leading views contained in 

 the following chapters was first promulgated 

 by the Author in an Essay entitled " A New 

 Theory of Terrestrial Magnetism," published 

 at New York in 1833; and somewhat ex- 

 tended in a series of papers in the Knicker- 

 bocker Magazine of 1834-5. The Author also 

 feels it due to himself, and to those friends 

 who have been long expecting this Work, to 

 state, that the first three books were originally 

 intended to be published separately, and were 

 actually printed in 1837, the preliminary chap- 

 ter excepted. But as more enlarged views of 

 the subject opened to him, he clearly perceived 

 that a development of the physiological and 



