CHEMICAL UNITS OF WEIGHT. FOKMUL^J 81 



a number of interesting and useful ideas. These were not indis- 

 pensable links in our reasoning, but, now that we have covered 

 the essential steps, a consideration of these ideas will be of great 

 value as a review of the subject and a means of mastering it 

 thoroughly. Formulae and their uses come up so constantly 

 in every part of the science that we must not omit any means of 

 securing a perfect understanding of them. The following chapter 

 is therefore devoted to restating in other ways certain parts of 

 the same subject. 



