Chemical and Physical Papers. 89 



rence of explosions, and what conditions may render them impos- 

 sible. 



The points covered were as follows: First, the method of min- 

 ing. The answers to this question confirmed the common belief 

 that explosions in long- wall mines are almost unknown. Our rec- 

 ords show only two cases. Second, the method of ventilation. 

 This question was asked with the idea of learning whether the 

 method of ventilation and the amount of air circulated in the mine 

 have any direct bearing upon the question. Third, the presence 

 or absence of gas. This question was asked with the idea of de- 

 termining whether explosions ever occur in mines in which the 

 presence of methane is not revealed by the ordinary methods of 

 examination. FouHh, the presence or absence of dust in the mine. 

 The answers to this question were expected to show to some extent 

 the relation of coal-dust to explosions. It was recognized, however, 

 that the replies would not be entirely satisfactory, because it is 

 only very recently that the possibility of dust explosions has been 

 widely recognized. Fifth, the presence or absence of water. This 

 question was asked for the purpose of learning whether explosions 

 have occurred in wet mines — that is, mines in which dust was not 

 dry enough to float in the air. Sixth, the explosive used. This 

 question was asked for the purpose of learning what, if any, con- 

 nection might exist between the employment of explosives and the 

 occurrence of explosions. As will be shown later, the connection 

 may be a very intimate one. Besides these specific questions, oth- 

 ers were asked which were intended to cover any points which 

 might not have been covered in the preceding questions, so that all 

 the conditions might be learned as far as it is possible to learn 

 them by this method. 



In addition to this a very large amount of literature has been 

 read, and abstracts have been made of the valuable parts. The 

 American literature on the subject has been quite thoroughly can- 

 vassed and a considerable amount of w ^k has been done on the 

 English, French and German publications. It was learned by this 

 investigation that much of the supposed knowledge of the subject 

 was not substantiated by such proof as to make it trustworthy, and 

 certain experimental work has been done to positively demonstrate 

 what was already believed to be true. 



The lines followed in the experimental work were determined* 

 by the conditions of the industry in this country. These condi- 

 tions are so well known that they may be dismissed with a word. 

 Almost all of the coal mined in this country is obtained by the 



