456 Mr, Faraday on new compounds 
c, that was also closed. The instrument now placed as at 
Fig. 2, had a and d cooled to o®, whilst the fluid collected in 
b was warmed by the hand or the air ; and when a portion 
had collected in d sufficient for the purpose, the whole instru- 
ment was immersed in water at 6o° ; and before the vapour 
had returned and been all dissolved by the liquid at 6, the 
pressure upon the gauge within was noted. Sometimes the 
fluid at d was rectified by warming that part of the tube, 
and cooling a only, the reabsorption at h being prevented or 
rather retarded, in consequence of the superior levity of the 
fluid at d, so that the first portions which returned to h lay 
upon it in a stratum, and prevented sudden solution in the 
mass below. This difference in specific gravity was easily 
seen upon agitation, in consequence of the striae produced 
during the mixture. 
Proceeding in this way it was found, as before stated, that 
the highest elastic power that could be obtained from the 
substances in the tube, was about 4 atmospheres at 6o® ; and 
as there seems no reason to doubt, but that portions of the 
most volatile substances in oil gas beneath olefiant gas were 
contained in the fluid, inasmuch as even olefiant gas itself is 
dissolved by it in small proportions, it may be presumed 
that there is no substance in oil gas much more volatile than 
the one requiring a pressure of 4 atmospheres at 6o°, except 
the well known compounds or, in other words, that there is 
not a series of substances passing upwards from this body to 
olefiant gas, and possessing every intermediate degree of 
elasticity, as there seems to be from this body downwards, to 
compounds requiring 250® or 300° for their ebullition. 
In reference to these more volatile products, I may state 
