INTRODUCTION V 



of the text, but it also rouses and holds the interest of 

 the reader. 



Though I have thus planned the series myself, the 

 work of writing each separate volume is done by others. 

 It is but just to these authors to say that in preparing 

 the facts for presentation they have spared no pains to 

 acquaint themselves with the work of the original inves- 

 tigators upon whose authority they rest. 



An illustration of the truth of this statement is found 

 in the volume on civics ( Town and City], in which pure 

 water is discussed. The author not only visited the 

 experiment station in Lawrence, Massachusetts, where 

 more scientific work has been done in sewage filtration 

 than elsewhere in the United States, but also made 

 careful study of water conditions in New York and other 

 American cities. 



Other subjects in the different volumes are treated 

 with similar thoroughness. In fact, the reference list 

 given with each volume although representing the best 

 available material for the use of teachers, gives but part 

 of that which was actually used in the preparation of the 

 books themselves. 



During the past few years important contributions 

 have been made to the fund of material bearing upon the 

 effects of the use of alcohol. These contributions have 

 come partly from scientific work in Germany, England, 

 and America, partly from recent careful investigations 



