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Tin-: SILO 15 



the lawn, rake the green grass into a heap, the larger the better. 

 Let it stand for two or three clays and note how hot it be- 

 comes down in the center of the heap. Well cured hay in the 

 mow produces some warmth by reason of chemical changes. 

 These carried to a certain extent give the pleasing aroma of 

 new hay and the flavor which cattle like. The warmth of the 

 hay mow is well known and liked by tramps. I once went into 

 the hay mow on a dark night to pitch down some hay for my 

 horse and the first thrust of my fork brought out a yell from a 

 sleeping tramp who had crawled in out of the cold and covered 

 himself in the warm hay. Most tramps have matches and a 

 pipe, and it seems more probable that fires in barns are due 

 to them than to the spontaneous combustion of heating hay. 

 The heating of any substance above i6o degrees either kills or. 

 greatly restrains the action of organisms which may be pres- 

 ent and hence the temperature of fermentation is self-limited. 

 Laboratory experiments show that hay will not kindle until 

 its temperature rises above a thousand or fifteen hundred de- 

 grees. It decomposes, chars and produces a vast amount of 

 smoke before it inflames. 



N-ew grain piled in elevators is liable to heat. Malting 

 grain gets hot. Cotton with the cotton seed left in, heats. 

 Linseed oil absorbs oxygen from the air and produces heat. 

 Cotton w^aste wdiich has been saturated with linseed oil and 

 piled up so as to admit air, but at the same time retain heat, 

 gets very hot. Insurance companies believe it may cause fires. 

 It would be a satisfaction to have the experiment tried and re- 

 ported. In a case like this wdien the chemical action is not 

 due to living organisms, the rise in temperature hastens the 

 process and spontaneous combustion is altogether conceiv- 

 able. Manure in piles gets hot, but the temperature is limited 

 to about i6o degrees because the heat is chiefly due to the 

 action of ferments which cannot live above that temperature. 

 Fermenting apple juice grows warm, but a temperature of 

 140 degrees would kill the yeast germs in it which make the 

 cider, and later a temperature of 104 degrees would kill the 

 acetic ferment which makes the vinegar. Chemical action 

 causes the heat of the human body, but we cannot endure 

 long a higher bodily temperature than 98.3 degrees, although 

 birds live normally at no degrees. Hence Pasteur said they 

 are immune from some of the germ diseases which attack us. 



