12 BULLETIN 763, U. S. DEPARTMENT OF AGRICULTURE. 
they should select carefully samples of milk and make the test to 
determine the value of the cows at home as butter-fat producers. 
The members of the class having Babcock testers at home should 
be required to make reports on the tests made. (Caution.—Too 
much emphasis can not be placed upon the danger of burns from the 
careless handling of sulphuric acid. Pupils should be warned to be 
very careful in handling it.) Give the pupils opportunity to test 
the milk at home regularly, and encourage them to combine the 
records of weighing milk at home with these tests at school to find 
the butter-fat production of each cow. 
Practical exercises—A junior cow-testing association may be 
organized among the members of the class. The cows at home may 
be tested by the class, observing the rules of the association and 
keeping records of same. 
Illustrative material—Construct charts showing the comparative 
amounts of butter fat in the milk of different cows; others showing 
the total amount produced in a given period; others showing the 
records of the best cows of the district. | 
Home projects.—Project A will require the testing of the milk of 
the dairy cows. For other projects, the weighing and testing of a 
dairy cow for a long or short period; the testing of the milk of a 
dairy herd and keeping the records. 
- Correlations.—Write up reports of the milk tests made at school 
and at home. Have the pupils make sketches of the parts of the 
milk-testing equipment, and charts showing quantity of butter fat 
in the milk of different cows. | 
Find how many pounds of butter fat in 3,000 pounds of milk 
testing 4.2 per cent. 
A farmer has 12 cows in his dairy herd, each averaging 25 pounds 
of milk daily. How many pounds of milk does he get in 30 days? 
If the milk tests 4.3 per cent butter fat, how many pounds pro- 
duced each day; for the 30 days? Find its value at.374 cents per 
pound. 
Develop similar problems from information gathered at home. 
LESSON V. RECORDS AND MARKETING. 
Sources of information.—State agricultural college bulletins. 
Topics for study.—This lesson follows naturally after the lessons 
on weighing and testing. The three are so closely related that one 
can not be taught successfully without the others. It would be the 
best thing for the teacher to teach these three lessons as parts of a 
wnit. 
Review briefly the methods of weighing and testing. Discuss the 
advantages of each. Suggest that neither could be of any permanent 
