vi Explanatory, 



peding the exposition of it. In the books on the 

 sciences, not only are acquired results stated, but as 

 full explanation as possible is given of the methods of 

 inquiry and reasoning by which these results have 

 been obtained. Consequently, although the treatment 

 of each subject is strictly elementary, the fundamental 

 facts are stated and discussed with the fulness needed 

 to place their scientific significance in a clear light, 

 and to show the relation in which they stand to the 

 general conclusions of science. 



Care is also taken that each book admitted to the 

 series shall either be the work of a recognized author- 

 ity, or bear the unqualified approval of such. As far 

 as practicable, authors are selected who combine 

 knowledge of their subjects with experience in teach- 

 ing them. 



