Calculation of Butter- and Cheese Yield. 187 



covered in the butter in different churnings, but since 

 the water and salt in butter are held mechanically and 

 are not chemically combined with it, the amounts re- 

 tained by the butter are quite variable in different 

 churnings, especially since the laws governing the reten- 

 tion of water in butter are but imperfectly understood. 

 213. Variations in the composition of butter. As 

 an illustration of the variations in the composition of 

 butter that usually occur, the analyses made in the 

 breed tests at the World's Fair in 1893 may be here 

 cited; the butter was in all cases made by as nearly 

 identical methods and under as uniform conditions as 

 could possibly be obtained by the skilled operators hav- 

 ing this work in charge ; the average composition of 350 

 samples of this butter, with upper and lower limits, 

 was as shown in the following table : 



Composition of samples of butter, World's Fair, 1893. 



Analyses of fifty samples of creamery butter taken in 

 1896, from the tubs ready for market at as many Wis- 

 consin creameries, showed that no two of them were ex- 

 actly alike in composition, but varied within the limits 

 given below: 1 



1 Wisconsin experiment station, bull. 56. 



