EXPLOSIONS FROM COMBUSTIBLE DUST. 163 



from the moisture in the materials. This steam would condense in the 

 meal and interfere with bolting, etc, if it were not removed. To effect 

 this another di-aught of air and another sjDOut are employed, and, as 

 might be expected, this current takes a large quantity of the very finest 

 flour, called flour-dust, with it. To save this a room is provided near 

 the end of the spout, called the flour-dust house. The spout conveying 

 steam and dust enters this room on one side, and another spout oppo- 

 site leaves it, passing to the open air. It is in this comparatively dead- 

 air space that the dust settles, and can be collected from the floor. 

 Here is some of this material, which, as you see, when blown into the 

 air, produces a vivid flash, extending from the table to the wall. 



The evidence taken before the coroner's jury shows very clearly that 

 it was this material that started the great explosion 

 of May 2d. Just how the mill took fire will prob- 

 ably never be known of course, but in all proba- 

 bility the stones either ran dry — that is, were 

 without any meal between them — or some foreign 

 substance, such as a nail, was in the feed, produ- 

 cing a train of sparks such as is produced by an 

 emery-wheel, or a scissors-grinder's wheel. These 

 sparks set fire to small wads of very hot dust, which, 

 as soon as they were fanned into a blaze, commu- 

 nicated it to the spout and house full of dust. An 

 eye-witness of the explosion first saw fire issuing 

 from the corner of the mill where this flour-dust 

 spout was situated, the end of the spout having 

 probably been blown out. This fire was followed 

 instantly by a quick flash, seen through all the win- 

 dows of the floor upon which the flour-dust houses 

 were situated, followed instantly by a flash in the 

 second story, then the third, and, in rapid succes- 

 sion, fourth, fifth, and sixth stories ; 

 then followed the great report pro- 

 duced when the immense stone walls 

 were thrown out in all four directions, 

 and the roof and part of the interior 

 of the mill shot into the air like a 

 rocket. ^ 



It would seem that a 

 blaze is necessary to ig- 

 nite the mixture, for I 

 have tried powerful elec- 

 tric sparks from a ma- 

 chine, and from a battery of Leyden-jars ; also incandescent platinum 

 wire in a galvanic circuit, and glowing charcoal, without producing 

 any fire, however thick the dust might be. Perhaps, however, under 



Fig. 3 



