EXPLOSIONS FROM COMBUSTIBLE DUST. 161 



I have here two boards, about twelve by eighteen inches, nailed to- 

 gether, forming a V {see Fig. 1). Just outside of the V an ordinary Bun- 

 sen's gas-burner is placed, and within is a small handful of dust taken 

 from a sash-and-blind factory. Upon blowing it smartly with the bel- 

 lows a cloud is formed about fifteen feet high — extending, in fact, to 

 the ceiling — which ignites from the lamp and produces a flash, very 

 quick and exceedingly hot, resembling very much a gunpowder-flash. 

 You will notice that a large amount of dust falls from all around the 

 edge of the flame without burning ; that is because it is not thick 

 enough. Two things are necessary : first, that each grain of dust be 

 surrounded with air, so that it can get the oxygen required instantly ^ 

 and, secondly, that each grain shall be so near its neighbor that the flame 

 will bridge over the space and pass the fire from particle to particle. 



I think, after seeing the immense flame produced by such a small 

 amount of fine saw and sand-paper dust, you will no longer wonder at 

 the rapid spread of flames in furniture and similar factories. You know 

 it is practically impossible to put out a fire after any headway is attained 

 in these establishments ; the draught produced will blow all the dust 

 from walls and rafters into the air, and the building in an instant is a 

 mass of flame. Perhaps many of you remember the fire in the East- 

 Side Saw-Mills, a few years ago. Large masses of fine sawdust had 

 probably collected upon the rafters, and the whole roof was perhaps 

 filled with cobwebs loaded down with dust. A fire started from one 

 of the torches used and shot through the mills with lightning-like 

 rapidity, and, save for the fact that the ends and sides of the building 

 were all open, there would have followed an explosion like that at the 

 flour-mills. As it was, the men had very great difficulty in escaping 

 ■with their lives, notwithstanding that a short run in any direction would 

 have taken them out of the mill. 



It is very evident that too great care cannot be taken to keep all 

 such factories and mills as free from dust as possible. 



I will now blow some ordinary starch into the air in the same Tvay, 

 and you notice the flame is more vivid than in the last experiment, and, 

 if you were in my position, you would notice that the heat produced 

 is much greater. Notice now that this powdered sugar burns in the 

 same way. 



You will see from the experiments further on that three-quarters 

 of an ounce of starch' will throw a box, weighing six pounds, easily 

 twenty feet into the air, and that half an ounce, burned in a box, will 

 throw up the cover three inches with a heavy man standing upon it. 



With these facts, which I have demonstrated before you, no one 

 need regard as a mystery the Barclay Street explosion in New York 

 city, where a candy-manufactory, in which large amounts of starch and 

 sugar might in many ways be thrown into the air by minor disturb- 

 ances, took fire and completely wrecked a building and destroyed many 

 lives. 



VOL. xiv. — 11 



