ON SPONTANEOUS INFLAMMATIONS* 217 



Thefe kinds of combuftion may be occafioned by different Caufes. 

 caufes, the principal of which are: 



1. Confiderable fridion. 



2. The adion of the fun. 



3. The difengagement of caloric, produced in bodies, which, 

 though not combullible, by being brought near to other com- 

 buftible bodies, may communicate fuch a degree of heat to 

 them, that they inflame by the conf a6t of the air. 



4. The fermentation of animal and vegetable fubftances 

 heaped up in a large mafs, which are neither entirely dry, nor 

 too wet, fuch as hay, dung, &c. 



5. The accumulation of wool, cotton, and other animal 

 and vegetable fubftances, covered with oily matter, particularly 

 drying oil. 



6. The preparation of linfeed oil for printers* ink, of var- 

 nithes, and in general of all fat. 



7. The torrefiaftion of different vegetable fubftances. 



8. The fu!phurated and pliofphorated hidrogen gafes which 

 are difengaged in many of the operations of nature, and of 

 which, the latter generally inflames by the fole conta(5t of at- 

 mofpheric- air, even at a low temperature, and which is often 

 feen at the furface of the earth like a fmal! flame, known by the 

 name of Jack ©'Lantern, in places in v\ hich there are animal 

 fubftances in a ftate of putrefaction; if oiher combuftibles are 

 met with where the difengagement takes place, they readily 

 catch fire. 



9. The phofphuret of lime and potafh, which maybe formed 

 in the preparation of charcoal, particularly in that from turf, 

 and from fome forts of wood which grow in marftiy (ituations. 

 This charcoal by being wetted, or by ftmply attrading the hu- 

 midify of the air, forms phofphureted hidrogen gas, which, by 

 theconta6t of the atmofpheric air inflames, and may fet fire to 

 the whole mafs of charcoal. 



10. The phofphorus which is fometimes, though rarely, 

 formed in the carbonifation of different forts of wood, without 

 combining either with lime or with potafli in the ftate of phof- 

 phuret. Thefe charcoals do not inflame fpontaneoufly at the 

 common temperature of the atmofphere, but they produce a 

 detonation by percufljon with nitrate of potalli, or with fome 

 other nitrates and metallic oxides to which the oxigen adheres 

 but feebly, and which, being in the.ftate of thermoxide, retain 

 much latent caloric. 



5 1 Fri6iion, 



