All Babcock centrifugal machines must be well 

 Machines. oiled and every part kept in good repair. The 



machine must be set on a firm foundation in 

 order to keep it free from vibration. It must be level and run at the 

 required speed. The correct speed for Babcock centrifugal machines 

 of different diameters is considered to be that stated in Farrington 

 and Woll's book, " Testing Milk and its Products," published by 

 the Mendota Book Company, Madison, Wisconsin. 



Babcock centrifugal machines and other appa- 

 Inspection, ratus used in making the test will be inspected 



at least once each year, the expense being borne 

 by the person or firm at whose plant the inspection is made. The 

 use of a machine that is out of repair or not in condition to give 

 accurate results, or the use of dirty or untested glassware, will be 

 considered sufficient grounds for re-inspection, or may lead to the 

 revoking of the certificate of the operator or prosecution at the dis- 

 cretion of the director of the experiment station. 



Glassware must be tested for accuracy by the 

 Glassware. Massachusetts experiment station before being 



used, and so marked as to indicate the fact. 

 It must be kept clean and in condition to insure accurate results. 

 Communications in regard to this law should be addressed to 



Philip H. Smith, 

 Mass. Agricultural Experiment Station, 

 Amherst, Mass, 



III. Suggestions for Making the Babcock Test. 

 PHILIP h. smith. 

 Attention is called to the following suggestions in regard to the 

 manipulation of the Babcock test, the slighting of which, in the haste 

 of commercial work, will tend toward inaccuracy. 



Composite samples of milk and cream should 

 Preservation of be preserved in clean, wide-mouthed, tightly 

 samples. stoppered bottles ; they should be well mixed 



after each addition to insure a uniform distribu- 

 tion of the preservative and its thorough incorporation with the 



