l62 



THE POPULAR SCIENCE MONTHLY, 



I will now burn in the same way some buckwheat, which, as j-ou 

 will observe, gives a very large blaze ; now some corn-meal, which is 

 too coarse to burn as well ; now some rye-flour, which burns much bet- 





Fig. 2. 



ter than the corn ; now some oatmeal, the finer part of which only 

 burns ; and so I might continue with all sorts of finely-ground vegetable 

 material. 



Let us take up now the produqts of the manufacture of flour from 

 wheat. There were between three and four hundred tons of these 

 materials, upon which I am now to experiment, in the Washburn Mill 

 at the time of explosion, and there was a corresponding amount in the 

 Diamond and Humboldt Mills, whicli, b}^ their sudden burning, pro- 

 duced the second and third shocks heard directly following the explo- 

 sion of the larger mill. 



The wheat is first placed in a machine where it is rattled violently 

 and brushed. At the same time a strong draught of air passes through 

 it, taking up all the fine dust, straw, etc., and conve^dng it through a 

 spout to a room known as the wheat-dust room, or perhaps more com- 

 monly it is blown directly out of the mill. 



You see some of this material here ; it looks like the wood-dust of 

 the first experiment, and, as you see, burns with a quick and sudden 

 flash when subjected to the same conditions. 



Here, then, we have the first source of danger in a flour-mill. A 

 thick cloud of this dust, when conveyed through a spout by air, will 

 burn in an instant if it takes fire ; and, if there is any considerable 

 amount of dust, as there would be if there were a dust-room, an explo- 

 sion will follow which may become general if it stirs up a thick dust- 

 cloud throughout the mill. 



The wheat after it has been cleaned in this way goes to the crush- 

 ers, which are plain or fluted iron or porcelain rollers, working like the 

 rollers in a rolling-mill. The object of these rollers is, I believe, to 

 break off the bran in as large pieces as j^ossible, and to crush out or 

 flatten the germ so that it can be separated with the bran from the rest 

 'of the meal. 



The crushed wheat goes now to the stones, where so much heat is 

 produced (average 135° Fahr.) that a large amount of steam is formed 



