272 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



one, other things being equal. It is difficult to make a com- 

 parison between the merits of the various types of silos in this 

 respect owing to the inability to find them under like condi- 

 tions. Freezing of silage is due to loss of heat; first, through 

 the silo wall; and second, to the air in contact with the feed- 

 ing surface. The first loss may be reduced by using a non- 

 conducting wall in the silo and the second by preventing the 

 circulation of air above the silage in the silo. 



It may be impartially said that, as far as the prevention of 

 freezing of silage is concerned, the stave, stone, single wall 

 brick and concrete silos are of about equal merit. Any kind 

 of an air space will partially prevent freezing, depending upon 

 how little the air circulates in this space and also upon how 

 much conducting material is required to tie the outer and inner 

 walls together. The King and Gurler silos were among the 

 first to make use of an air space to prevent the loss of heat 

 through the walls, but the air spaces were so deep that circu- 

 lation of air from the top to the bottom of the wall was quite 

 free and readily transmitted heat from wall to wall in this 

 manner. 



Cement blocks have more or less material extending from 

 wall to wall which acts as a direct conductor. In double wall 

 brick silos it is necessary to have a header course occasionally 

 to bind the two walls together. The clay pipe silo has consid- 

 erable material extending from wall to wall. The construc- 

 tion of the walls of the Iowa silo are such as to thoroughly re- 

 strict the circulation of air, but like those previously mentioned 

 has considerable material connecting the two walls. The ratio 

 of this material to the air space is about one to four, but tile is 

 a rather poor conductor of heat. When properly made the 

 double wall concrete silo is perhaps the most nearly frost proof 

 of all. The conducting material between the walls consists only 

 of small metal ties and the circulation of air may be cut off by 

 the insertion of horizontal tar paper partitions. 



The second cause of freezing mentioned, that is, the loss of 

 heat from the silage surface, is too often the cause of unneces- 



