On Spontaihcous Inflammations. 347 



air even at a low temperature, and which often presents ii- 

 selfatthe surface of the earth like a small flame, kno.wii 

 under the name of ivill-xvitk-the-icbp, in places where am- 

 nial substances in a state of putrefaction have been buried ; 

 if there are other combustibles at that time on the sspot 

 where the discno-agcment takes place^ they may readily be 

 kindled. 



9th, Phospliuret of lime and of potash which may be 

 formed in the preparation of charcoal, eepecially in that of 

 turf and some sorts of wood vvhich grow in marshy placps, 

 This charcoal, when wet, or by merely attracting the mois- 

 ture of the atmosphere, forms phosphorated hydrogen, 

 which by the contact of the atmospheric air inflames^ and 

 niav set fire to the wbole mass of charcoal. 



10th, The phosphorus which is sometimes formed, though 

 rarely, in the carbonization of difllrent kinds of wood, with- 

 out bein;!; con)bmed either with lime or potash in the state 

 of phosphuret. This charcoal docs not inflame sponta- 

 ncously'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 ox\gen 

 wcaklv adheres, and which are found in a state of thcim- 

 oxide retaining a great deal of latent caloric. 



1. Fricl'ion. 



It is generally known that two bodies when rubbed againr-t 

 each other become heated. The intensity of the heai pro- 

 duced depends on several circum.Uances, and varies chiefly 

 in the ratio of the duration of the friction, and of the na- 

 ture and surface of the rubbed bodies. If the friction takes 

 place between combustible bodies, such as wood, the heat 

 it excites n)ay often be suPricient to inflame it ; if the bodies 

 are not combustible, such as stones, or little combustible, 

 as metals, they do not inflame themselves; but they may 

 communicate to other combustible bodies around them such 

 a deerce of heat that the latter will inflame by contact with 

 the atmospheric air. 



D. Falcani repeated the experiments long known for ob- 

 taining fire by the friction of two pieces of wood, giving to 

 one of the rubbing pieces the form of a tablet, and to thc^ 

 other that of a spindle or cylinder: the result of some ot 

 these experiments will be sufficient to show, that,i!i the con- 

 struction of machines and instruments, more attention ought 

 to be paid to the choice of the wood destined to be exposed 

 ^o malual friclion. 



