PREFACE. 
THE science and practice of Dairying is constantly broadening. 
The different phases of this industry cannot now be mastered in so 
short a time as years ago, when comparatively little was known 
about the principles upon which dairying is now securely based. 
In connection with the teaching of dairying in the special 
four-year course at the Iowa State College, a set of lectures on 
advanced butter-making was prepared. In compiling these 
lectures special endeavors were exerted toward embodying the 
principles of butter-making, as well as the best practice of this 
art, in this as well as in foreign countries. 
The authors have studied, by personal observation and 
practice, the best and most progressive methods employed in 
butter-making in the principal dairy countries of the world, and 
have endeavored to incorporate these in this work. In con- 
nection with this practical phase of the question, the authors 
have endeavored to give such related scientific information as 
may be of interest and value. The general scientific knowledge 
has been absorbed from time to time from work done by various 
investigators at the different Experiment Stations. To all of 
these men who have searched for and discovered facts bearing 
upon dairying, the authors wish to express thanks and acknowl- 
edgment. 
The statistics and tables given in this work have been quoted 
from noted reliable authorities as indicated. 
The authors believe that the subject of dairying should no 
111 
