112 



Such admixture is probably imperfect in practice, but even if 

 great care were always taken some interval of time must elapse 

 between such mixing and the actual withdrawal of the small 

 quantity to the purchaser. 



A question therefore arises : How long may milk stand at 

 rest without making the part withdrawn differ appreciably 

 from the bulk? 



Among other things the rate at which cream rises to the 

 surface of milk depends on the temperature, but the control of 

 temperature presents difficulties. The water supply on many 

 farms is insufficient for effective cooling, and many customers 

 will not accept milk unless it is warm. Even if the milk has 

 been cooled and customers are willing to accept it cool, the 

 sun's heat during transit cannot always be avoided. 



These considerations suggested an experiment on the varia- 

 tion of the composition of milk due to sampling and the 

 opportunity of the presence of the Dairy class was taken to 

 carry out such an experiment. The samples were taken under 

 the supervision of Miss Maidment, Dairy Instructress for the 

 County of Durham. A four gallon vessel with a tap at the 

 bottom was about three quarters filled with milk and samples 

 drawn from the bottom tap, or taken from the top at intervals, 

 and subsequently analysed in the Chemical Department. 



Inspection of the results given in tables A, B and C will 

 show at once that when high temperatures prevail even a few 

 minutes' rest suffices to give useless samples, but that when 

 low temperatures prevail the danger is smaller. 



Whilst these experiments add but little to what was known 

 before, they serve to emphasise the difficulties of sampling 

 milk, and in consequence the difficulties of dealing in milk. 

 This commodity is so different from other farm produce that 

 the properties of milk demand from its producers a special 

 study. 



