41G Abstract Report of Afjricultural Discussions. 
tendency to hasten the process. By doing this, I am inclined to 
think that conceutra'ted food like cotton-cake, or bean-meal, or rape- 
cake, would be rendered more digestible — more readily available 
for the prodiiction of milk of a good quality. 
Time does not allow me to speak at length of the influence of 
various lands of food on the dairy. I will therefore, in conclusion, 
only direct the attention of the members of the Society to the dif- 
ferent modes of testing the quality of milk. 
We have instruments — lactometers, as they are called — made for 
this purpose ; but these lead frequently to erroneous conclusions, 
being most of them based on erroneous principles. The com- 
mon lactometer, which is in effect a float, when immersed in milk, 
indicates by its position the strength of that liquid. Milk which 
is more dense keeps the float higher : milk which is less dense 
allows it to sink lower : when water, therefore, is mixed with milk, 
the float will sink deeper. But there is one consideration which has 
here to be taken into account. It is this — that the bvitter in the 
cream is lighter than the whey of milk. Cream, I find by direct 
determinations, has a specific gravity of 1'012 to 1*019. It vai'ies 
slightly. It is a little heavier than water, but lighter than the whey 
of milk, or skimmed milk. Milk rich in cream would, therefore, be 
lighter than milk poor in cream. By this lactometer an extra quantity 
of cream in milk is indicated in precisely the same way as an extra 
quantity of water. In short, this instrument, which measm-es the 
density of milk, furnishes very incorrect results. I cannot, perhaps, 
make this clearer to you than by giving one or two determinations. 
In testing the sj^ccific gravity of good milk, I foimd it as follows :— 
1"030 to 1"032. By skimming off the cream the gravity is increased. 
The lactometer, again immersed in the skimmed milk, now rises five 
divisions, and indicates 1"037. But if I take off from this milk the 
cream, and then put 10 per cent, of water to it, I get again precisely 
the same specific gravity which the new milk originally indicated, 
namely, 1"032. I believe that the adulteration most commonly prac- 
tised in large towns consists in taking off the cream, and then, if the 
milk be particularly good, adding a little water. This is not indi- 
cated by the common lactometer. To meet this objection attempts 
have been made to construct a lactometer on totally different prin- 
ciples. If the milk is put into a graduated glass and allowed to settle, 
some of the cream rises, and the quantity can then be read off. In 
good milk I find from 10 to 12 jier cent, of cream by volume ; in poor 
milk there is sometimes as little as from 6 to 7 per cent. These 
instruments give more useful results than I at first expected, and are 
useful as a means of making comparisons. 
Temperature has some influence on the separation of the cream, but 
not so great, according to my exjieriments, as is generally believed. 
When the temperature is about 50", most of the cream is separated 
from the milk in from eighteen to twenty-fom- hours ; and about 
7-lOths per cent, of fatty matter remains in the skimmed milk. 
However long you may keep milk at rest, it is impossible to separate 
the cream completely ; and if the process be conducted at a temperature 
