THE CONSTRUCTION OF MODERN SILOS 771 



the men ascended by steps, and the grain, when wanted, was chap. 

 taken out from a door at the base." XVI - 



It is important to note that the early silos were used prin- 

 cipally for the preservation of corn and other dried cereals, for 

 indefinite periods, and there are instances of corn having been 

 preserved in good condition for the long period of 200 years. 

 On the other hand, the silos of the present day are used more 

 particularly for the storage of green fodder, to provide food for 

 cattle during the winter months, or for a year at most. Food 

 thus preserved may, however, be kept indefinitely, provided 

 that air is not allowed to enter the silo. For this reason it is 

 important that the sides and floor should be perfectly air-tight, 

 and it is also essential that the sides be smooth and vertical, so 

 that the silage may settle uniformly and compactly, leaving no 

 vacant spaces for the accumulation of air. 



The word " silo," taken from the Greek "siros" — a pit for 

 holding grain — is the name now applied to any air-tight 

 chamber formed for the preservation either of dried grain or 

 green food. It may be simply a trench or pit dug in the 

 ground in any dry position, into which the silage is filled and 

 weighted down with planks, earth, or other material. More 

 commonly it is a structure of wood, metal, brick, stone, or 

 other building material, or a combination of these, built en- 

 tirely above ground or extending down only a few feet, and 

 standing either by itself or forming a part of the other farm 

 buildings. The origin of structural silos on the modern plan 

 is of very recent date, but the progress of siloing has been so 

 rapid and successful— in America, at any rate— that in the 

 short period of thirty years, over a hundred thousand silos 

 were built in the United States alone, and the number is 

 steadily increasing. 



744. Form.— \n form the silo may be built either square, 

 rectangular, octagonal, or circular on plan. If forming part of 

 a scheme of buildings its shape would probably be decided by 

 the position it occupied and the space available, but if standing 

 alone, either form could be adopted at will. The round silo 

 (Fio- 241) is more favourable to the even and compact settling 

 of the silage owing to the absence of corners and, consequently, 

 more favourable to its perfect preservation. On the other 

 hand it does not fit in with other buildings so readily and with- 



49* 



