INTRODUCTION IX 



sulphate in 500 cu. cm. of water; also 180 g. of Rochelle salt 

 and 70 g. of sodium hydroxide in 500 cu. cm. of water. Mix 

 equal volumes of the two solutions just before using. Of 

 course any fractional part of this amount may be prepared. 



Part of the exercises of this manual have been gathered from 

 existing sources; all have been simplified for the use of first-year 

 students. The writer found many helpful suggestions for the 

 exercises on "Soils" in a pamphlet entitled "Some Principles of 

 Agriculture," presumably published by the Connecticut State 

 Board of Education. 



J. C. H. 

 Decatur, Illinois. 



