A CASE OF SPONTANEOUS COMBUSTION. 



39 



in rain water, oxygen is in its most active form under natural 

 atmospheric conditions, and oxidation of combustible matter 

 takes place more rapidly in its presence. 



This pile of black shale had all of the conditions and essen- 

 tials for spontaneous combustion. The high content of com- 

 bustible material in the shale, such as marcasite, pyrite, oil and 

 bituminous matter, furnished the fuel for the fire. The rain 

 water with its high oxygen content and the air slowly circu- 

 lating through the pile, supplied the oxygen for oxidation. 

 The shale was a poor conductor of heat so that the heat from 



Burning of Chattanooga shale in the Tennessee River near Hamburg, from 

 spontaneous combustion. 



oxidation was not lost through radiation but accumulated 

 within the pile. 



The marcasite in a finely divided condition and, to a less ex- 

 tent, the pyrite, was very readily oxidized by the moist air and 

 by the rain water with its high oxygen content, clinging to the 

 surface of the marcasite just above the water line. This was 

 the starting point of the spontaneous combustion. The heat 

 produced by the oxidation of the marcasite was retained by the 

 shale and thus enhanced the oxidation. In this way the rate 

 of oxidation kept increasing and the heat accumulating. As the 



