Lactometers 79 
pose; but it was soon found that the percentage of 
cream depends not so much upon the amount of fat 
present in the milk as upon the size of the globults 
and the conditions under which they are brought 
to the surface, and that the percentage of cream 
does not necessarily bear a constant relation to the 
percentage of fat. 
Specific gravity.—The determination of the spe- 
cific gravity was next brought into use as a means 
of determining the quality of milk. Inasmuch as 
milk is slightly heavier than water, and as water is 
the most common adulterant of milk, any addition 
of water to it would serve to lessen its specific 
gravity, and would easily be detected by a determi- 
nation of the specific gravity. To determine the 
specific gravity of milk, various forms of specific 
gravity hydrometers, known as- lactometers, have 
been devised. They were formerly very much more 
depended upon as a test of the quality of milk than 
at present, and though now we have learned that 
under certain conditions a simple specific gravity 
test may not only be inaccurate, but entirely mis- 
leading, still they are of considerable use for cer- 
tain purposes.and in connection with certain other 
instruments. 
Lactometers.—In devising the lactometer, it was as- 
sumed that 1.029 was as low as the specific gravity of 
any unadulterated milk would ever fall; therefore a 
hydrometer was devised, the scale of which was gradu- 
ated from 0 to 120, the 0 marking the point of pure 
water, or a specific gravity of 1.000, and 100 cor- 
