USE OF THE GALACTOMETER. 165 



oules of butter or fat are enveloped in casein or 

 curd, and are a very little lighter than the milk ; if 

 it is left undisturbed, they therefore rise slowly to the 

 surface, and form cream. If the milk be much agi- 

 tated and stirred about, the cream will be much 

 longer in rising ; so also if it is in a deep vessel, as 

 a pail, in place of shallow pans. Warmth promotes 

 its rising. 



a. There is a little instrument called the galacto- 

 meter, intended to measure the richness of milk. 

 This consists of a series of graduated tubes, which, 

 by means of small divisions, mark the thickness of 

 cream that rises to their surface. It is not a correct 

 instrument, for the reason that I have already stated, 

 that cream does not rise so well through a deep 

 column of milk as through a shallow one. The 

 quantity of cream then, indicated by a galactometer, 

 will always fall short of the real proportion which 

 the milk contains. It may sometimes be of use, for 

 comparing the richness of milk from various cows of 

 the same dairy. 



When milk is drawn in the usual way from the 

 cow, the last of the milking is much the richest : this 

 is because the cream has, in great part, risen to the sur- 

 face inside of the cow's udder; the portion last drawn 

 off then, of course contains the most of it. Such a fact 

 shows the importance of thorough and careful milk- 

 ing. In some large dairies, the last milkings from 

 each cow are collected in a separate pail. More 

 milk is said to be obtained from the same cow when 

 she is milked three times a day, than when but once 

 or twice ; less when milked once than twice, but in 

 this last case it is very rich. 



Some large breeds of cows, are remarkable for 

 giving very great quantities of poor watery milk : 

 other small breeds give small quantities of a milk, that 

 contains an uncommon proportion of cream. These 



