34 Introduction. 



On this basis, if a cow evaporates from her body four 

 pounds of rain she must expend the equivalent of the solids 

 of 3.39 pounds of milk. 



A wet snow-storm is often worse for animals to be out 

 in than a rain-storm, because in this case the snow requires 

 melting as well as evaporating, and the number of heat 

 units per pound of snow is 



142.65 -f 966.6 = 1109.25 heat units, 



and the heat value of a pound of milk is barely sufficient 

 to melt and evaporate a pound of snow. 



47. Cooling Milk with. Ice and Cold Water. If it is de- 



sired to cool one hundred pounds of milk from 80 F. 

 down to 40 F. it is practically impossible to do so with 

 water in the summer season in Wisconsin. It is difficult 

 even to cool it as low as 48 F. for most of the well and 

 spring water has a temperature above 45 F. and much 

 of it is above 50 F. If lower temperatures than 48 F. 

 are desired during the warm season some other means 

 must be resorted to. Since it requires 142 heat units to 

 melt a pound of ice, one pound is capable of cooling from 

 80 to 40 F. 



of milk, 



supposing the specific heat of milk to be the same as that 

 of water, which is not quite true. To cool 100 pound? of 

 milk from 80 F. to 40 F. will require, therefore, about 



100 

 -=26| Ibs. of ice, 



O. IJ 



supposing it to be used wholly in cooling the milk. 



If the water has a temperature above 40 F. before the 

 milk and ice are placed in it, there will be required enough 

 more ice to cool the water down to the temperature desired 

 for the milk. 



The greatest economy in the use of ice will be secured, 

 therefore, when the creamer contains just as little water 

 as will cover the cans and give the needed space for the ice, 



