of Flame and Gases. 407 



to expect that a certain bulk of expanded air would be less 

 sensible in its diamagnetic effects than an equal bulk of denser 

 air ; just as one would anticipate that a vacuum would present 

 no magnetic or diamagnetic effects whatever, but be at the 

 zero point between the two classes of bodies (Experimental 

 Researches, 2423, Sl^l-). It is certainly true, that if the air 

 were a body belonging to the magnetic class, then its expan- 

 sion, being equivalent to dilution, would make it seem dia- 

 magnetic in relation to ordinary air (Experimental Researches, 

 2367, 2438) ; but that, I think, is not likely to be the case, 

 as will be seen by the results described further on in reference 

 to oxygen and nitrogen. 



If the power conferred by heat is a direct consequence, and 

 proportionate to the temperature, then it gives a very remark- 

 able character to gases and vapours, which, as we shall see 

 hereafter, possess it in common. In my former experiments 

 (Experimental Researches, 2359, 2397) 1 heated various dia- 

 magnetic bodies, but could not perceive that their degree of 

 magnetic force was at all increased or affected by the tempe- 

 rature given to them. 1 have again submitted small cylinders 

 of copper and silver to the action of a single pole, at common 

 temperatures and at a red heat, with the same result. If 

 there was any effect of increased temperature, it was that of 

 a very slight increase in the diamagnetic force, but I am not 

 sure of the result. At present, therefore, the gaseous and va- 

 porous bodies seem to be strikingly distinguished by the power- 

 ful effect which heat has in increasing their diamagnetic con- 

 dition. 



As all the experiments, whether on flame, smoke, or air, 

 seemed to show that air had a distinct magnetic relation, which, 

 though highly affected by temperature, still belonged to it at 

 all temperatures ; so it was a probable conclusion that other 

 gaseous or vaporous bodies would be diamagnetic or mag- 

 netic, and that they would differ from each other even at com- 

 mon or equal temperatures. I proceeded therefore to examine 

 them, delivering streams of each into the air, in the first in- 

 stance, by fit apparatus and arrangements, and examining the 

 course taken by these streams in passing across the magnetic 

 field, the magnetic force being either induced or not at the 

 time. 



In delivering the .various streams, I sometimes introduced 

 the gases into a globe with a mouth and also a tubular spout, 

 and then poured the gas out of the spout, upwards or down- 

 wards, according as it was lighter or heavier than air. At 

 other times, as with muriatic acid or ammonia, .1 delivered the 

 streams from the mouth of the retort. But as it is very im- 



