

156 REporT OF THE DIRECTOR OF THE 
twenty-four hours, and the other half twelve hours before 
skimming. | 
As the result of fifty- -six days’ experiment, it was found that the 
milk which stood for twenty-four hours gave upon an average — 
18.93 per cent of its weight of cream, while the milk which stood 
twelve hours, gave upon an average 20.17 per cent of its weight 
in cream. 
Now we have shown as the average of 465 analyses of morning’s 
milk, and an equal number of samples of the evening’s milk, that 
the average milk yield in the morning was 8.16 pounds, and in 
the evening 8.21 pounds; also that the average per cent of fat in 
the morning’s milk was 4.26, and in the evening’s milk it was 
4.22 per cent. 
It will be seen, therefore, by simple calculation, that the total 
fat of the morning’s milk was to that in the evening’s milk as 100 
to 99.67, while the amount of cream from the morning’s milk which 
had set twenty-four hours, was to that from the evening’s milk 
which had set but twelve hours as 100 to 106.55. 
This difference is obviously due to the fact that after the cream 
has practically risen, upon longer standing it shrinks in volume 
owing to the separation of a portion of the skim-milk from the 
lighter fats. It shows, however, the fallacy of estimates based ~ 
alone on the number of spaces of cream which different samples 
of milk may furnish. 
Upon an average it will be seen that ‘the fat “lobia in the 
lower strata of milk must rise about one and one-third inches 
per hour, but owing to the minuteness of these globules, their 
apparently slow progress is indeed relatively very rapid, since it 
requires the smaller globules, represented as less in diameter 
than one division of the micrometer scale, to move each second 
over a space 200 times greater than the diameter of the 
elobules. 
Should we suppose a balloon twenty-five feet in diameter to 
rise with equal relative velocity, it would rise about one mile per 
second. Se 
But the relative rapidity of the rise of the globules diminishes 
as their diameter increases, and the number of their diameters in 
distance through which the several sized globules measured, by 

