i9i 2.] Summary of Agricultural Experiments. 945 



proof of this, however, since he was not able to obtain living pieces 

 of grass free from bacteria. The action of the living plant must 

 be restricted to the initial stages of heating, since grass is killed at a 

 temperature of 40 0 to 45 0 C, whereas the temperature reached by 

 hay in the stack amounts commonly to 70 0 to 8o° C. 



It was found that heating could not take place in the absence of 

 oxygen, but neither was steam-sterilised hay capable of spontaneous 

 heating. 



At the same time, a rise in temperature was obtained when a little 

 ordinary hay was added to the sterilised, showing that the presence of 

 micro-organisms is one of the factors necessary for the heating. Fur- 

 ther evidence in support of a biological explanation as against a purely 

 chemical one was afforded by the fact that hay moistened with for- 

 maldehyde or chloroform quite lost its self-heating capacity. The great 

 absorption of oxygen by the hay at high temperatures and the produc- 

 tion of carbon dioxide is taken as a proof of nothing more than that 

 at high temperatures (after self-heating has been accomplished) oxida- 

 tion takes place, leading to the stack catching fire, and the purely 

 chemical nature of this latter phenomenon would seem to be doubted 

 by no investigators. 



Several different bacteria were isolated by Dr. Miehe, the most 

 active of which was B. calf actor. This bacillus was found specially 

 active between 40 0 C. and 70 0 or 75 0 C, above which temperature the 

 heating is no longer 'due to biological conditions. A second bacillus 

 (B. coli) was isolated, which caused a rise in temperature in dead hay 

 from 18 0 C. to 42 0 C. It is not claimed by Dr. Miehe that heating 

 between these temperatures is caused solely by this bacillus, as two 

 other organisms were found able to cause heating, viz., Oidium lactis 

 and Aspergillus niger, the former causing a rise to 58 0 C. and the 

 latter to 43 0 C. 



The writer's findings as to the causes of the heating of hay are 

 summarised as follows : — 



(1) Up to 40 0 C. (104 0 F.) heating is chiefly due to B. coli, or if 

 the grass is not quite dead the first stage is caused mainly by respira- 

 tory activity. 



(2) From 40 0 C. (104 0 F.) to 75 0 C. (167 0 F.) B. calfactor is mainly 

 responsible. 



(3) Above 75 0 C. (167 0 F.) the heating is purely chemical. 

 Necessary conditions to heating are the presence of moisture and 



a supply of oxygen. Bacilli can only develop in moist substances, 

 and a water content of the hay of 25 per cent, was found sufficient 

 to lead to considerable temperatures. The larger the stack, the higher 

 will be the temperature of the interior. 



Feeding Value of Varieties of Mangolds (Univ. Coll., Readin'g, Dept. 

 of Agric. and Hort., Bull, xii.).- — A comparison was made of Golden 

 Tankard and Prizewinner Yellow Globe mangolds in regard to the total 

 dry matter per acre produced. Both varieties were grown on four 

 farms, and twenty-five average sized roots from each plot were analysed. 

 The percentage of dry matter in Golden Tankards varied at the different 

 centres from 12*75 to I 4' I 5> anQl m Prizewinner Yellow Globes from 

 9*90 to 1 2*40. Thus six tons of Golden Tankard had approximately 

 the same amount of dry matter as seven tons of Prizewinner Yellow 



3 T 



