ON SPONTANEOUS INFJ^AMM ATIONS. 239 



of more efficacy and lefs danger might be fubftituted, Ihould 

 «t lead be careful not to inclofe the bran in the cloth, either too 

 hot or too much roafled. 



Brewers, after having made their barley and other grain, 

 which they employ in making beer, germinate, dry it in a 

 kiln, except what is intended for pale beer, and they gene- 

 rally roaft it more or lefs highly, to give the beer a deeper 

 or paler colour. If, therefore, when the grain is brought 

 from the kiln, it is put, fiill hot, into facks, it frequently hap- 

 pens that it heats and takes fire, and this has eccafioned feve- 

 ral fires in breweries. 



8. Sulphurated and phofphorated Hidrogen Gay. 



The caufe of fubterraneous fires and volcanoes is generally Inflammation of 



attributed to the decoropofition of pyrites, or metallic ful ■ ^"'PJ"""'^^ f "^ 

 1 1 • 1 • . ■ • r t 1 ^. /- . phofphorated hi- 



phurets, buried m the interior ot the earth. Thele pyntousdrogengas. 



mafles are decompofed by the contacSl and concurrence of water 

 and air, and the decompofition is always accompanied by a 

 great expanfion of caloric, and a difengagement of a very in- 

 flammable gas, called fulphurated hidrogen gas. This gas in- 

 flames at an elevated temperature, and can communicate the 

 inflammation to the fulphur of the pyrites, to the coal and other 

 bituminous matters which generally accompany it. 



Similar inflammations are fometimes obferved near coal-pits. 

 In exploring the coal, veins and infulated mafles of pyrites are 

 frequently met with : fince thefe pyrites always communicate 

 a bad quality to the coal, the miners generally lay Ihem afide, 

 and throw them out of the pit : if thefe heaps of pyrites, 

 mixed with coal, are then expofed to the alternate aftion of 

 the fun and rain, they heat and inflame. Great care muft 

 therefore be taken that thefe accumulations of pyrites fliould 

 be kept at a diftance from all combuftible bodies to which they 

 would neceflarily communicate the inflammation. 



There are many operations of nature in which fulphurated 

 hidrogen gas is formed, but it often enters into other combina- 

 tions as it forms, it diflblves in water, or difengages at a tem- 

 perature too low for it to inflame. 



By boiling phofphorus in a folution of potafli or lime, phof- 

 phorated hidrogen gas is difengaged, which, being much more 

 combuftible than fulphurated hidrogen gas, inflames at a low 

 teoiperature as foon as it comes in contact with atraofpheric air. 



This 



