INTRODUCTION Vll 



tions is not studying chemistry ; he should master the 

 principles governing the combination of elements and 

 then the memorizing of chemical formulas becomes un- 

 necessary. In the preparation of the lessons, there are a 

 number of reference books which should be consulted 

 occasionally. For example, if difficulty is experienced 

 with the subject of valence and radicals, the interesting 

 chapter upon these topics in Ellen H. Richards' 

 " Chemistry of Cooking and Cleaning" should be read. 

 Remsen's "Chemistry," Hart's "Chemistry for Begin- 

 ners," Storer and Lindsay's "Elementary Manual of 

 Chemistry, ' ' as well as many others, will be found valuable. 

 In studying the parts relating to foods, crops, and ani- 

 mal feeding, Henry's "Feeds and Feeding," Jordan's 

 "Feeding of Farm Animals," Armsby's "The Principles 

 of Animal Nutrition," " Johnson's How Crops Grow," 

 and " How Crops Feed," and the bulletins of the U. S. 

 Department of Agriculture and of the several stations 

 should be available. The student should early acquire the 

 habit of consulting other works, as many topics are pre- 

 sented more clearly in one work than in another. 



He who studies chemistry from a professional point of 

 view, as medical chemistry, pharmaceutical chemistry, 

 or agricultural chemistry, should remember that because 

 of the limited time for the subject in professional schools, 

 he is receiving at the best only a very abridged course in 

 the science. Hence the necessity of supplementing the 

 work by collateral reading and study ; otherwise he comes 

 into contact with only one phase of the subject, and 

 while he receives a technical education, he may obtain 



