2-1% On Spontaneous Inflammations . 
5th, the accumulation of wool, cotton, and other ani- 
mal and vegetable substances, covered with an oily mat- 
ter, and particularly a drying oil. 
6th, The boiling of linseed oil for printers ink, of var- 
nish, and in general of every fat matter. 
7th, The torrefaction of different vegetable substances. 
8th, Sulphurized and phosphorized hydrogen gas dis- 
engaged in several operations of nature, the last of which 
in particular inflames merely by the contact of the atmos- 
pheric air even at a low temperature, and which often 
presents itself at the surface of the earth like a small 
flame, known under the name of ivill-with -the -wisp, in 
places where animal substances in a state of putrefaction 
have been buried : if there are other combustibles at that 
time on the spot where the disengagement takes place, 
they may readily be kindled. 
9th, Phosplmret of lime and of potash which may be 
formed in the preparation of charcoal, especially in that 
of turf and some sorts of wood which grow in marshy 
places. This charcoal, when wet, or by merely attract- 
ing the moisture of the atmosphere, forms phosphorated 
hydrogen, which by the contact of the atmospheric air 
inflames, and may set fire to the whole mass of charcoal. 
10th, The phosphorus which is sometimes formed, 
though rarely, in the carbonization of different kinds of 
wood, without being combined either with lime or potash 
in the state of phosplmret. This charcoal does not inflame 
spontaneously at the common temperature of the air; 
but it may produce a detonation when struck with nitrate 
of potash, or some other nitrates or metallic oxides to 
which oxygen weakly adheres, and which are found in 
a state of thermoxide retaining a great deal of latent 
caloric. 
1. Friction . 
It is generally known that two bodies when rubbed 
against each other become heated. The intensity of the 
