5S 
Account of an Explosion 
flour was heated to such a degree, that a boy who went 
into the warehouse could not remain there, so much were 
his feet scorched by the heat ; this flour was of a dark 
brown colour, and whilst the people were examining it, 
sparks began to appear, and fire spread itself around, 
without producing any flame, like a true pyrophorus.* 
He also informed me, that an inflammation like that 
above-mentioned had happened at the house of a baker 
in this city, called Joseph Lambert ; it was occasioned 
by shaking some large sacks, which had been filled with 
flour, near a lighted lamp, but the flame, though pretty 
brisk, did not do any mischief. 
According to the foregoing accounts, it appears to me, 
that it is not difficult to explain the phenomenon in ques- 
tion. The following is the idea I have conceived of it : 
as the flour fell down, a great quantity of inflammable air, 
which had been confined in its interstices, was set free ; 
this, rising up, was inflamed by the contact of the light ; 
and, mixing immediately with a sufficient quantity of at- 
mospheric air, the explosion took place on that side 
where there was the least resistance. As to the burning 
of the hair, and the skin, of the boy who was in the 
warehouse, the cause of it must be attributed to the fire 
of the fine particles of the flour, which, floating in the 
atmosphere, were kindled by the inflammable air, in the 
same manner as the powder from the stamina of certain 
vegetables, (particularly of the pine and of some mosses) 
when thrown into the air takes fire, if any light is appli- 
ed to it. 
But it may be objected, that as the flour was not at all 
* I was very anxious to ascertain by experiments, whether it were possible to 
bring flour alone into the state of pyrophorus, but it was in vain ; for though I 
calcined flour with a strong heat, in a small retort, with the same precautions as 
are used in making other pyrophoric I never could succeed in making it take 
fire by exposure to the air. By joining alum with it I obtained a true pyropho- 
nis, as Lemery had already done. 
