2.58 Prof. M. C. Potter. Bacteria as [Jan. 
matter, and such substances remain unsusceptible to change only so long as 
bacterial action is excluded. 
It is quite evident that where there is surface exposure bacteria must play 
a large part in the disintegration of coal, which is one of the most insoluble 
substances known, and that these organisms form an invaluable agency in 
assisting the circulation of carbon and again converting it to the uses of 
Nature. 
Summary. 
Under conditions of exposure to the air, a slow oxidation of amorphous 
carbon takes place through the agency of bacteria. This has been conclu- 
sively established by experiments upon such carbonaceous substances as 
charcoal, lamp-black, coal, and peat. 
When these substances are subjected to Petal action carbonic acid is 
given off, as estimated volumetrically by absorption in baryta solution and 
titration with standard oxalic and hydrochloric acids. : 
The amount of COz given off increases in proportion to the rise of tempera- 
ture and ceases to be evolved at a supra-vital temperature. There is no 
evolution of CO. under perfectly dry conditions such as preclude the possi- 
bility of bacterial life. 
A distinct rise of temperature occurs through the action of bacteria. The 
heat generated was determined by measurement, with a galvanometer, of the 
electromotive force produced by the difference of temperature between two 
thermo-elements, one placed in a sterile and the other in an inoculated flask. 
The evolution of CO, and the accompanying rise of temperature does not 
take place when carbonaceous substances are preserved from the intrusion of 
micro-organisms. 
The heat generated by microbial activity 1s an influence to be taken into 
account in connection with the oxidation and spontaneous combustion of coal ; 
it may be a dangerous motive force acting upon explosive gases. 
The oxidising action of bacteria must be largely responsible for the 
disintegration of coal and the high percentage of depreciation which it 
undergoes in store. 
Coal and peat, hke other organic matter, are lable to decomposition as 
soon as conditions are presented suitable for the life of aerobic organisms. 
The carbon is then once more liberated in the form of COs to play its rdle 
in the life cycle. It is thus conceivable that the vast supplies of carbon 
locked up in the world’s coal-fields may become available for plant nutrition 
without the intervention of direct combustion. 
