xvi REFORMS IN CONDITIONS OF SUPPLY 289 



4J- hours the temperature of the milk only increased by 4'4 

 degrees, although the air temperature throughout was high. 



Good milk-cooling apparatus can now be readily obtained. 

 They are either of the flat or of the cylindrical type. The 

 cylindrical type is not much used except for cream cooling. 



The milk passes in a thin stream over a coil of pipes 

 through which a stream of cold water passes from below upwards. 

 In large milk depots the milk coolers are often of double form ; 

 the milk passing over the upper part is cooled by water, and 

 then passes over the lower part and is cooled by a saline 

 mixture to a still colder temperature. The milk is damaged 

 if too suddenly chilled to a very low temperature. 



The degree of cooling of the milk depends upon 



() The initial temperature of the milk. 



(6) The extent of surface exposed to the cold water. 



(c) The temperature of the cooling water. 



(d) The slowness of the passage of the milk. 



Three points may be mentioned in regard to the use and 

 care of milk coolers : 



(1) Since the milk passes over the surface of the cooler, \ 

 it is important that the cooler be fixed in a clean place and ( 

 supplied with pure air. (The writer has found a milk cooler 

 in a large milk factory fixed directly above an untrapped 

 drain.) 



(2) The water used for cooling should be pure. This is 

 not unimportant, since occasionally leaks occur and the water 

 gains access to the milk. 



(3) . They must be cleaned thoroughly directly after use, 

 while immediately before use they should be looked to, and if 

 necessary again washed. 



It is of importance that water should not be left in the 

 coolers after use. This prolongs their life, while in frosty 

 weather this precaution is essential. 



B. THE TRANSIT OF MILK 



In the smaller towns the milk purveyor, who may be the 

 farmer himself, usually has his cart ready waiting to take the 

 milk and distribute it. The milk destined to supply the large 

 towns has usually to be -sent by rail. Sometimes it is sent 



u 



