THE EARTH'S BOUNTY 



as such, it is one of the chief ingredients of 

 cheese, constituting about one-fourth of that 

 important food. The albumen may be co- 

 agulated by heat. The mineral matter in 

 milk, called ash or salts, is the part that re- 

 mains when milk is evaporated to dryness and 

 burned. This consists chiefly of phosphates 

 and chlorides of soda, potash, and lime. 



It is well known that when suga-r is dis- 

 solved in water, the solution is less limpid 

 than pure water, and if many small bodies, 

 a very little lighter than water, were thor- 

 oughly mixed into the solution, their rise 

 would be more or less retarded by the sticki- 

 ness of the surrounding fluid. Milk might 

 be compared to a thin sirup, with many fatty 

 and light particles floating in it, as just de- 

 scribed. It is viscous, or sticky, because of 

 the solids held in solution and suspension; and 

 this viscosity, together with fibrin, has a con- 

 siderable effect in retarding the rise of the fat 

 globules and the formation of the cream layer. 

 The older milk is, the more effective are these 



177 



