142 Agricultural Experiment Station, Ithaca, N. Y. 



It will be seen that the milk aerated with the Powell aerator 

 kept no lon<»er than that which had not been aerated. That 

 which was aerated by the Champion and Star aerators kept for a 

 constant bnt not very long time longer than that which was not 

 aerated. This difference in favor of the aeration is considerably 

 less than we had expected to obtain; bnt there were several 

 conditions that are likely to have made this difference less than 

 it would be nnder ordinary circumstances. In the first place the 

 air in which the milk was set was comparatively uniform in tem- 

 perature and free from, contaminating odors; in the second place 

 only a short time elapsed after milking and aeration, so there 

 was little chance for contamination in the stable. Then again 

 all the surroundings of the cattle were kept as neat and clean 

 as could well be done. We believe that under the conditions 

 that affect most dairies tlie good effects of aeration would be 

 more pronounced than those we obtained. But we are inclined 

 to regard as extravagant the statement recently made, in a lead- 

 ing agricultural paper, that "aerated milk will keep at least 

 three times as long as non-aerated." 



The question is often raised whether milk that is intended for 

 butter-making may be aerated and the cream afterwards success- 

 fully separated by the gravity process. Four trials were made 

 in which the milk that had been aerated was set in Cooley cans 

 at forty degrees side by side with milk of the same lot that had 

 not been aerated. In all cases the temperature of the creamer 

 was 4040, and the milk set twenty-four hours. The results 

 were as follows: 



Aerated, aA^erage per cent of fat in skim milk 53 



Not aerated, average per cent of fat in skim milk 31 



It will be seen that while there was some loss in the efficiency 

 of the creaming of the aerated milk, it was not very great. What 

 is remarkable is that the aerated milk suffered no fall of tem- 

 perature after it was placed in the creamer, and was more effi- 

 ciently creauied than the diluted milk set at sixty degrees 

 (table I), where the fall of temperature was 30-35 degrees. This 

 seems to be in direct contradiction to the theory which supposes 

 that the fall of temperature after the milk is set is one of the chief 

 factors in complete creaming by the deep-setting gravity process. 



HENRY H. WING. 



