152 ELEMENTARY AGRICULTURAL CHEMISTRY 



prevents the evolution of heat ; the second is efficacious cliiefly 

 by carrying the heat away as it is evolved, and thus keeping 

 down the temperature. 



The pleasant odour of hay, upon which its palatability 

 chiefly depends, is partly due to compound ethers and other 

 fragrant products of fermentation, and partly to coumarin, 

 CjjHgOg, which is present in \v oodi-vuE [A sperula odoraia), in 

 Bokhara clover [Melilotus alba), and in sweet-scented vernal 

 grass (Anthoxanthum odoratum). Though the odour of 

 coumarin is generally considered pleasant, there is some 

 reason to think that horses and cattle are not very fond of it. 



AvEBAGE Composition op Hay. 



Ensilagfe, or Silagfe. — When green fodder is closely com- 

 pacted so as to prevent access of air as much as possible, 

 fermentation is hindered and restricted, and the fodder may 

 be kept for some time. Originally all silos were pits or 

 buildings of stone or wood, intended to be air-tight, in which 

 the fodder could be oubjected to great pressure. The simpler 

 plan of merely stacking the green fodder in the open, treading 

 it well, and finally weighting it with stones or earth is now 

 often adopted. 



