158 
British Dairy Farming. 
1 in 10,000, i.e., which is sufficiently strong to coagulate ten 
thousand times its bulk in liquid of ordinary milk at 95 degrees 
in 40 minutes. On the Continent this formula is more easily 
understood by reason of the decimal system, the cubic cen- 
timetre being a ten-thousandth part of ten litres. 
Upon the basis of these figures my friend, Dr. Jacopo Rava, 
of the Reale Stazione Experimentale at Lodi, in Italy, has con- 
structed an algebraical formula which giyes the golden number 
of 40,000 as a key to ascertain the strength of a rennet, the 
quantity of milk which can be coagulated, the quantity of rennet 
which must be used, and the time it will be employed under 
certain giyen conditions. These formulae I have carefully 
worked out and amplified, and I belieye they will be found to 
be of considerable seryice in the cheese-making industry. First, 
in order to find the strength of a giyen sample of rennet, the 
number of litres of milk to be used (a gallon is 4^ litres) must 
be multiplied by 40,000, and the result divided by the number 
of cubic centimetres of rennet, and the minutes occupied in coagu- 
lation. Thus, supposing 48 gallons (216 litres) of milk is coagu- 
lated in 60 minutes by the use of 18 cubic centimetres of rennet, 
we can ascertain the strength of this rennet as follows : 
(40,000 X 216) ~ (18 X 60) = 8000. 
In order to ascertain how much milk can be converted into 
curd with a given quantity of rennet of a known quantity, and 
in a fixed time, it is necessary to multiply together the quantity 
of rennet by the time to be occupied in coagulation, and by 
the strength of the rennet, and afterwards to divide the sum 
obtained by 40,000. Let us suppose that we wish to ascertain 
how much milk can be coagulated in 60 minutes, with IS centi- 
metres of rennet of a strength of 8000. This is the actual 
strength shown by Mr. F. J. Lloyd of the rennet of Messrs. 
Fullwood and Bland in the Dairy Show competition. We get 
the following formula : ' 
(18 X 60 X 8000) 40,000 = 216 litres, or 48 gallons. 
When it is necessary to ascertain the quantity of rennet 
necessary for a given quantity of milk, the number 40,000 is 
multiplied by the number of litres of milk, and the result 
divided bv the sum obtained bv multiplying the number of 
minutes the curd is setting and the strength of the rennet. 
Thus : 
(40,000 X 216) -f- (60 X 8000) = 18 cubic centimetres. 
To find the time which would be employed in coagulating a 
given quantity of milk, with a given quantity of rennet of 
known strength, it is necessary to multiply the number of litres 
