MEANS OF DETERMINING THE QUALITY OF MILK. 603 
exercises on the indications of the lactometer, Dr. Hassail, 
who has made the analysis of very numerous specimens of 
milk, makes the following remarks : 
“ It is stated,” he says, “ that the addition of a small 
quantity of warm water to milk increases the amount of 
cream ; the belief in the accuracy of this statement is entirely 
erroneous; the addition of water to milk does not increase 
the quantity of cream; it merely facilitates and hastens, in 
a most remarkable manner, its formation and separation, as 
is shown by what follows:—Six lactometers were filled, one 
with pure milk, the remainder with the same milk diluted 
respectively with 10, 20, 30, 40, and 50 per-centages of water. 
In twenty minutes the lactometer containing pure milk 
showed but half a degree of cream, in forty minutes it 
showed 4°, and at the end of twelve hours it showed 9°. The 
instrument containing 50 per cent, of water showed in twenty 
minutes 6° of cream, in forty minutes 6|°, and at the end 
of twelve of hours 5°. The rapidity with which the cream 
was thrown up on the other four tubes—viz., those contain¬ 
ing 10, 20, 30, and 40 per-centage of water was proportion¬ 
ally great ; the two extreme cases have been quoted merely 
in order to exhibit more prominently the results which 
were obtained.” It thus appears, continues Dr. Hassall, 
“ that the addition of a large quantity of water to milk oc¬ 
casions an almost immediate formation of cream, but does 
not augment the amount; of this fact, in some cases it 
would be an advantage to dairymen to avail themselves. 
The addition of water to milk of course lessens its specific 
gravity, and so facilitates the ascension of the cream.” 
Now, it would appear from this experiment that we are 
warranted in deriving a conclusion quite opposed to that just 
quoted. Here we have 100 parts of pure milk exhibiting 9° 
of cream, while 50 parts of the same milk mixed with 50 
of water are found to yield 6J° of cream. But the relative 
proportion of cream existing in the pure and diluted milk is 
as 2 to 1, while the proportion separable from the two fluids 
respectively are shown by the lactometer to be as 1*385 to 1 
(9 to 6|). It is plain, therefore, that the per-centage announced 
by this instrument is not a true index of the richness of the 
fluid examined. With regard to the hydrometer, or specific- 
gravity instrument, it is almost unnecessary to say that 
experience has long since shown it to be quite inappli¬ 
cable as a means of ascertaining the purity of milk. The 
normal density of milk has been variously stated by writers, 
some placing the average density at about 1029, others at 
1038, others, again, at some intermediate number. But, 
