PEAL, 



~2- 



SC. ENCtS 

 LIBRARY 



PREFACE. 



THE work here offered to the public will be found 

 suited, it is hoped, to two classes of readers. There 

 is a numerous class of intelligent persons who do not 

 find it convenient to possess themselves of all the more 

 important conclusions of the physical sciences by a re 

 sort either to original memoirs or to formal scientific 

 treatises, but who nevertheless recognize the great inter 

 est of the developments of recent science, and would be 

 glad to be put in a position to take a panoramic survey 

 of its grand generalizations. Such an opportunity the 

 author has aimed to present. 



The work will also be found useful as an aid in re 

 view. The student may plod ever so diligently and ever 

 so intelligently through the details of a science; he is 

 apt to gain only vague impressions and floating ideas, 

 unless enabled to take a comprehensive survey of the 

 field, with the details all left in the background, and the 

 great outlines and prominent landmarks all brought sa- 

 liently into proper relations to each other. As the en 

 gineer, who may have completed the most elaborate sur 

 vey of a region, requires at last to contemplate it from 

 some elevated hill-top to gain a vivid conception of the 

 landscape as a whole, so the student needs to be lifted 

 up to a position where he may enjoy a bird s-eye view 



