I 69 ] 

 XVII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



xxFTER the vacation for the holidays, the Society met on the 

 9th of January, and at this and a subsequent meeting on the 16th 

 it was occupied with the reading of New Researches upon Flame, 

 by Sir Humphry Davy, whicli are of a most singular and interest- 

 ing nature. 



Sir H. Davy divided his New Researches upon Flame into four 

 parts. In the first he considered the effects of rarefaction by the 

 air-pump, and of condensation on flame. In the second he ex- 

 amined the phicnomena of rarefaction by heat, in relation to flame 

 and combustion. In the third, the effects of the mixture of ga- 

 seous sul)stances not concerned in combustion or flame. And io 

 the fourth he described various practical and theoretical appli- 

 cations of the results of his researches. Rarefaction by remov- 

 ing pressiue he finds, contrary to the opinion of Grothers, has 

 no influence on combustion, except in relation to the heat pro 

 duced in rarefied atmospheres. Comi)ustion continues in rare 

 atmospheres as long as sufficient heat is produced in the process 

 to effect the combination of oxygen with the inflammable basis : 

 and the degree of rarefaction at which flames are extinguished is 

 different for every species of flame : — those that require little 

 heat for their combustion burn in much rarer atmospheres, and 

 likewise those that produce much heat in their combustion. 

 Carburetted hydrogen, which requires a strong heat for its com- 

 bustion, and which produces comparatively little heat, is extin • 

 guished in an atmosphere rarefied only four times ; whereas sul- 

 phur, which requires very little heat for its combustion, burns in 

 an atmosphere rarefied 20 times ; and pliospliorus, which re- 

 quires only a common temperature for its combustion, burns in 

 an atmosphere rarefied (iO times. By heating atmospheres or ex- 

 plosive mixtures which have ceased to support combustion, or to 

 exp]odc from rarej'aclion, combustion or explosion may be made 

 to take place. Sir H. Davy's general conclusion in tlie first sec- 

 tion is, that, whether the atmosphere be rarefied or condensed, 

 combustion takes j)lace at the same temperature in it ; and that 

 the diminution or increase of heat, from the smaller or larger 

 quantities burning in rare and condensed atmospheres, are the real 

 causes of the extinction, diminution, or increase of combustions 

 in them. 



In the second section Sir II. shows, in direct opposition to 

 Grothers, that expansion by heat uniformly increases the combus- 

 tibility of gaseous mixtures. Me states a fact particularly cu- 

 rious and interesting from the application he has made of it in 



E '<i another 



