152 DESCRIPTION OF FEEDING STUFFS 
ciently heavy to largely exclude the air in the siloed fodder and 
thus secure a good quality of silage. In case of deep silos the loss 
from spoiled silage on the top is smaller in proportion to the amount 
of silage stored, and a smaller loss occurs while the silage is being 
fed out. As the silage packs better j in a deep silo than in a shallow 
a : Sanne. one, the former kind of silos 
_ will hold more silage per cubic 
"| foot than the latter (Fig. 28). 
e| 3. The silo must have 
smooth, perpendicular walls, 
which will allow the fodder to 
settle without. forming cavities 
along the walls. In a deep silo 
the fodder will settle several 
feet during the first few days 
after filling. Any unevenness 
in the wall will prevent the 
mass from settling uniformly, 
and air spaces thus formed will 
cause the surrounding silage 
to spoil. 
The walls of the silo must 
be made rigid and very strong, 
so as not to spring when the 
siloed mass settles. The lateral 
(outward) pressure of cut corn 
when settling at the time of 
filling is considerable, and in- 
creases with the depth of the 
: silage, at the rate of about 
Fia. 28.—A good concrete silo costs more 
than a wooden silo, but will last indefinitely eleven pounds per square foot 
when properly cared for, and needs no atten- a : 
tion beyond an application of a coat of pure for every foot in depth of sil- 
cos oe two or three years. (Wis- age. At a depth of 20 feet 
thers is, therefore, an outward 
pressure of 220 pounds per square foot ; at 30 feet, a pressure of 330 
pounds. It is because of this great pressure that it was difficult to 
make large, rectangular silos deep enough to be economical, since 
the walls of rectangular silos always spring more or less under the 
pressure of the silage, and this seldom kept as well in them as it 
does in those whose walls cannot spring. In the round wooden silos 
every board acts as a hoop, and, as the wood does not stretch much 
lengthwise, there is but little danger of spreading of such walls; it 
