On Spontaneous Inflammations. 343 



ether substances, which without being oily are very unc- 

 tuous to the touch. 



•2. Action of the Sun. 

 The strongest heat is produced, all sorts of combustibles 

 are kindled, and the most refractory substances are fused 

 by exposure to the sun's rays concentrated by means of 

 lenses or concave mirrors. It may happen that other bodies 

 are in such a condition as to produce without our will the 

 effects of lenses and of burning mirrors : though these ef- 

 fects are rather physical than chemical, it is of importance 

 to make them known, in order to guard against the dano-er 

 of them. We have instances of fires produced by glass de- 

 canters filled with water and exposed to the sun in an 

 apartment. When the form of the vessel is nearly similar 

 to that of a lenticular or spherical glass, the rays are re- 

 fracted, and produce, by uniting in the focus, a heat capa- 

 ble of setting fire to combustible bodies placed in it, 



3. Heat excited in non-comlustille Bodies. 



It is well known that quicklime immersed in water, or 

 merely moistened, produces a considerable degree of heat. 

 It has even been employed with success for heatin-^^ at a 

 small expense apartments, hot-houses, hot-beds, &c. ^This 

 property which quicklime has of disengaging a great deal 

 of caloric by contact with the air, and that no less dangerous 

 of dissolving and corroding animal substances immersed in 

 it, require the greatest precautions where considerable de- 

 puts ot quicklime are formed. To preserve it, care must 

 be taken to guard it from the contact of the air, and from 

 moisture of every kind ; and particularly to remove from its 

 neighbourhood all combustible bodies, such as wood, hay, 

 ?traw, &c., which might inflame spontaneously should the 

 lime contract the least humidity. The Juvrnal de la Haute' 

 Sao/ie ga\c an account last year of the burning of a barn, 

 one of the partitions of which being v/ood had caught fire, 

 because a heap of quicklime, mtended for rcpalnng the 

 farm-houocs, had been carelessly thrown against it. 



A great number of similar pha?.notTiena take place in na- 

 ture, where bodies, by changijig their composition, or con- 

 tracting new combinations, become so he.iied, or disenciee 

 so much calorie, that other combustible substances around 

 them may be inflamed. 



4. Fermentation of Animal and Fcgciahle Substances. 

 Most animal and vegetable substances, if heaped upon 



each 



