260 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



deep. A larger percentage of mouldy and otherwise inferior 

 silage is found near the top of a silo than at the center or near 

 the bottom, proving that a certain weight is necessary to com- 

 press the silage and exclude the air so as to insure its perfect 

 preservation. By building a deep silo a greater percentage of 

 good silage is obtained, which is, of course, a matter of econ- 

 omy. Good practice at present seems to indicate that the depth 

 should be at least 30 feet. Some limitation in height may be 

 necessary in silos of light construction on account of the wind 

 or the strength of the walls to resist crumpling, but in masonry 

 silos greater height than the average is advisable. A large 

 percentage of good silos are built considerably deeper, even 50 

 to 60 feet. In the discussion of foundations, it is stated that 

 they should extend below the frost line. If the earth inside 

 the foundation wall is excavated to this depth and the floor 

 placed on a level with the footings, a very cheap addition to 

 the silo is secured without increasing the height of the silo 

 above the ground. Beyond a certain depth the difficulty in 

 removing the silage is so great as to more than balance the 

 economy of securing additional space in this way. Three or 

 four feet up to the first door is not considered objectionable. 



The capacity of a silo varies as the square of the diameter, 

 while the wall surface varies directly as the diameter. This 

 means that as far as capacity is concerned the silo should 

 be of as large diameter as possible. But there are other limit- 

 ing factors involved. When silage is left exposed to the air 

 for a short time, more than a day, it spoils. Enough must 

 be removed daily so that it will keep fresh. In well settled 

 silage, the air does not penetrate much over an inch, and if 

 iy 2 to 2 inches are fed from the surface daily the silage will 

 remain fresh. In warm weather the spoiling will take place 

 much more rapidly than in cold weather, requiring that silage 

 be removed from the surface to a greater depth each day in 

 order to keep it fresh. It has been noticed also that air pene- 

 trates into loose, fery silage farther than it does into that which 

 is moist and compact. Thus, it is seen that under some cir- 



