CHAP. viii. THE SILO. 848 



draw off the moist heated air and to introduce a fresh supply. As the 

 introduction of fresh air to an already fermenting mass supplies it 

 with the oxygen necessary to feed the ferment, it is easy to understand 

 that the principle is wrong, and that failure was inevitable. After 

 several stacks, and the machinery used upon them, had been destroyed 

 by fire, the exhaust fan system died out, leaving behind it a prejudice 

 against new notions. 



But the process of excluding air rested on a sound basis, and the 

 few who were bold enough to experiment in this direction were 

 rewarded with success. New converts were made, and, though the 

 opposition was great, even from those who were accredited with being 

 in the best position for estimating the value of the process, yet in a few 

 years it emerged from the experimental stage, and became an 

 established farm practice. The earlier English literature of ensilage 

 shows that there were many misconceptions as to the principles, as well 

 as errors in the practice, and these militated against its popularity. It 

 was considered absolutely necessary that the silo, or receptacle for the 

 green herbage, should be in the form of an air-tight chamber, for it 

 was supposed that were any air allowed to enter the silo the whole of 

 the contents would be injured. It was also thought that, as vertical 

 pressure must be applied, there would be a corresponding lateral 

 bulge ; and so great was this lateral pressure imagined to be that it was 

 supposed that ordinary walls would be deficient in strength to resist it. 

 As a means of ensuring the necessary resistance it was considered that 

 underground chambers would be most economical. Hence, the earlier 

 silos were made underground. In some cases pits were dug purposely, 

 and in others advantage was taken of those already in existence, such 

 as chalk-pits. 



Again, as it was thought that very great pressure was necessary, 

 expensive methods of applying weight were used. It was also regarded 

 as imperative that the material to be ensiled should be chaffed. It 

 was further deemed necessary that the silage should be made in wet 

 weather, and it was considered that ensiling was only a means of saving 

 fodder which would be otherwise wasted. There were, moreover, 

 doubts as to the safety of feeding animals on silage. All these objec- 

 tions have, however, disappeared. 



It is not indispensable that an air-tight chamber should be used, 

 although such a silo is most perfect, notwithstanding that the pack- 

 ing at the sides requires great care. No silos are in reality absolutely 

 air-tight, except those made on principles similar to the silos of Mr. 

 Whitehead, of Paddockhurst, Sussex, who devised circular chambers, 

 built of brick, partly above, and partly below ground. They are made 

 about twenty feet in depth, and are covered with an iron dome-shaped 

 top, with a small opening in the middle for the purpose of filling. The 

 opening is closed by an iron plate which is screwed down into a bed 

 lined with india-rubber, so as to ensure a perfectly air-tight condition 

 The silo can also be filled at side doors, which are likewise made air- 

 tight by being bedded in india-rubber ; these doors are convenient for 

 emptying the silo. The herbage is chaffed so as to pack in more 



