PROGRESS IN AGRICULTURAL EDUCATION. 293 



Study 24. — Using the Babcoch test for butter fat. 



Because of its simplicity, accuracy, and ease of operation, the Babcock test has 

 become the standard test for determining the value of milk and cream as delivered to 

 the cheese factories and creameries all over the country. It is also largely used by 

 private individuals who keep cows, to determine whether a cow pays for her keeping 

 or not. 



A good tester can be obtained from almost any dairy-supply dealer at a small cost. 

 Directions for using come with the machine. Have some pupil bring a sample of milk 

 from one of the cows at home. The sample should be taken after the milking is done 

 and the milk has been poured two or three times from one bucket to another, so as to 

 be thoroughly mixed. (Make a note of how much the cow gave at that milking, 

 either weigh or count a gallon as 8| pounds.) Take about a half cupful as a sample 

 and put into a clean bottle. From this bottle the sample is drawn for testing, after 

 mixing the contents of the bottle thoroughly. 



Having determined the per cent of butter fat in the sample, an estimate can be made 

 of the total amount of butter fat in the milk from which the sample was taken. Make 

 several tests of the same cow's milk, using both morning and evening milk. Note 

 variations. Estimate how much milk this cow gives in a year and calculate the niim- 

 ber of pounds of butter fat produced. A poimd of fat in ordinary practice should make 

 about 1.1 pounds of butter. What price per pound do you get for butter? Does the 

 cow pay for her feed? The cow should not be condemned until many tests have been 

 carefully made, and you are sure you are right. 



Test samples of skim milk, buttermilk, and cream. Determine the amount of fat 

 lost in different methods of separating cream, e. g., separator, shallow pan or crocks, or 

 deep cans set in cold water. 



If you are in a dairy district, or where people are interested in making their cows 

 pay for their keeping, this exercise will furnish work for several weeks and may be 

 made profitable to your patrons as well as to your pupils. The making of a test of a 

 few samples need not occupy more than a half hour and the cost of each test is less than 

 one cent. 



Study 25. — The effect of temperature on the creaming of milk. 



Select two bottles of the same size and shape; quarts are large enough, preferably 

 with long slanting necks and made of white glass so that the layer of cream may be 

 seen. Have some one of the children bring enough milk to fill both bottles. This 

 milk should be milk drawn on the morning of the day on which it is brought, if pos- 

 sible. Mix thoroughly, preferably by pouring from one vessel to another two or three 

 times; then fill both bottles to within an inch of the top, place one in a pail of water at 

 a temperature as near 40° F. as possible, and put where it will stay near that tempera- 

 ture. Put the other bottle in a pail of water at a temperature of 75° F. and keep it 

 there. At the end of two hours, and each two hours throughout the day, measure with 

 a ruler or a strip of paper the depth of the cream line on each bottle. 



Notice the difference in the depth of the cream line, and whether it increases or 

 decreases as the bottles stand. On which one does the line stand most clearly? Why 

 does cream rise? Can you explain the difference in the effect of the two conditions 

 of temperature? 



Note. — This last point is a disputed question, but you are entitled to your own opin- 

 ion. What does this exercise teach you about setting milk away for the cream to rise? 



