New York AGRICULTURAL EXPERIMENT STATION. pil. ( 
eurd. The curd is then heated gradually to a temperature of 
about 98° F.. The rapidity of heating and the extent of heating 
are points which the judgment of the maker must determine. 
During the heating, the curd is kept in constant but gentle 
agitation. This heating causes each piece of curd to shrink 
and expel moisture, whereby it becomes more firm and dry. 
In regard to the details of this shrinking and drying action, 
much remains to be learned, but it-is probably due to the com- 
bined action of heat, of rennet, and of lactic acid. After the 
temperature has reached about 98° F., the heating is discon- 
tinued and the curd is stirred only at intervals sufficient to pre- 
vent its packing on the bottom of the vat. When the curd has 
become sufficiently firm and dry, it is allowed to settle and the 
whey is drawn off. To tell exactly when is the proper time to 
draw the whey from the curd requires the very best judgment 
of the maker, for this is one of the most critical points in the 
manufacturing process. Here, cultivated sense of smell, touch, 
taste and sight is needed. The most common test used to deter- 
mine the proper time to draw off the whey is known as the iron- 
test. A portion of curd is squeezed in the hand, then placed 
against a hot iron, and carefully drawn away from the iron. If 
the curd sticks to the iron and is drawn out in little threads, 
about one-fourth of an inch long, the whey is generally ready to 
be drawn; if the threads are shorter, the action is continued 
until a satisfactory test is obtained. This test is supposed by the 
cheese-maker to indicate the amount of lactic acid present. That 
it is a rough test for the relative amount of acid present, our 
experiments showed conclusively. The curd acquires the prop- 
erty of being drawn out into threads, probably by action of rennet 
rather than of acid. It is stated that in milk coagulated by acid 
alone the curd does not acquire the property of being drawn into 
threads. bie 
After the whey is drawn from the curd, the process of manu- 
facture may be varied, one method of treatment making what is 
known as a stirred-curd cheese, and the other method a Cheddar 
cheese. We will briefly describe each of these procosses. 
(5.) Stirred-curd cheese.— After the whey has been drained from 
the curd, the curd is stirred and kept broken up so as to prevent 
packing. . It is kept at a certain temperature, until certain signs — 
