If milk is to be set for cream, the sooner it is put to rest and the
less heat it looses before setting, the better for the separation of
the cream. If cooled down much, the cream will rise more slowly and
separate more imperfectly. In cooling, the fluids and semi-fluids
condense faster than the fats, and hence become relatively heavier, and
settle as the fat globules rise, by virtue of the law of gravitation.
The theory has been broached by Mr. H.B. Gurler, of DeKalb, Illinois,
that in sudden cooling, the fluids and semi-fluids are not only
condensed, but the fats expanded, thus increasing the difference in
specific gravity in both directions. In this way, the rapid rising of
cream in sudden cooling he thinks may be better accounted for. His
idea is based on the fact that water, just before congealing, begins
to expand and continues to expand as the temperature lowers. Fats
consolidate at a much higher temperature than water, and he thinks the
same law of expansion may intervene in both cases. So far as we are
aware, it is not known whether fats do actually expand before and after
reaching the point of congelation or not, and we shall feel an interest
in having the question positively settled by the scientists. If it is a
fact, it introduces a new element into our philosophy, and will help in
the solution of some points not yet satisfactorily determined.