that a correct scale of the comparative yield of butter at
different temperatures might be arrived at; as thus: From a very low
degree of temperature little or no butter; from a temperature of about
38 degs., 16 oz. from 16 quarts of milk; ditto, 45 degs., 21 oz. from 16
quarts of milk; ditto, 55 degs., 26 to 27 oz. from 16 quarts of milk."
This is a higher yield of butter than, I suspect, most dairymen get: but
Mr. Horsfall's cows being of the best kind for milking, and well fed,
the milk is, of course, rich in butter; and his experiments prove that
even the richest milk will not throw up its butter unless at a certain
temperature.

In the churning of cream the motion should be slow at first until the
cream is thoroughly broken up. In churning milk the agitation should
neither be violent nor irregular; about 40 or 50 motions of the plunger
or board per minute will be sufficient. In steam-worked churns the
motion is often excessively rapid, and the separation of the butter
is effected in a few minutes; but the article obtained in this hasty
way very quickly becomes rancid, and must be disposed of at once. An
hour's churning of sour cream appears in general to produce good butter.
Sweet cream and whole milk require a longer period--the latter about 3
hours--but in any case prolonged churning is certain, by incorporating
cheesy matter with the butter, to produce an inferior article.

Sweet milk becomes sour, evolves a considerable quantity of gas during
churning, and its temperature ascends four or five degrees. Oxygen is
unquestionably absorbed, and it is probable that a portion of the sugar
of milk is converted into acid products.

I have already stated that even the most carefully prepared butter
contains a small proportion of casein and sugar of milk. This casein
is the good genius of the cheese-maker, but the evil genius of the
butter manufacturer. How? In this way:--When butter containing a
notable proportion of casein and sugar of milk is exposed to the air,
the following changes take place: the casein passes into a state of
fermentation, and acting upon the sugar of milk, converts it, firstly
into the bad-flavored lactic acid, and secondly into the bad odorous
butyric, capric, and caproic acids. The first of these compounds in a
state of purity emits an odor resembling a mixture of vinegar and rancid
butter; the second possesses an odor resembling that of a goat--hence
the name _capric_; the third has an odor l