2o6 Mr, Delaval on the Caiife of the 



I Ihall not here enter upon the confideration of 

 any other aeriform fluids, becaufe they are foreign. 

 to my prefent inquiry. 



I was led to an examination of the inflammable 

 principle, by the changes, which it operates in 

 coloured fubftances, both when it is in a detached 

 and feparate ftate, and when it forms a conftituenc 

 part of fixed air, and is diff ufcd throughout the 

 atmofphere. 



Fixed air has been frequently confidered as a 

 mere compound of air, and phlogifton. But, fuch 

 a compound feems to approach nearer, in its 

 nature, to phlogiflicated air; as it is deficient in 

 one of the principles, which is eflential to fixed 



air. 



1 have endeavoured to point out fome qualities 

 of the inflammable principle, which have not 

 hitherto been obferved, or which have not been 

 applied to the folution of the pha;nomena of 

 elaftic fluids. Such are, its folvent power; its 

 power of effecting the mildnefs, and cryftallization 

 of alcalies; its ftrong affinity to calcareous earth, 

 alcalies, and other fubftances which yield fixed 

 air, whofe fimilar, and correfpondent, properties 

 refult from the phlogifton, which it contains as a 

 conftituent part. 



I willingly fubmit thefe obfervations,to thecan-r 

 did judgment of thofe excellent philofophers, who 

 have extended the knowledge of elaftic fluids, by 

 their inftruftive labours: amongft which, the 



numerous 



