474 



In concluding the details of these experiments, the author considers 

 that they all tend to prove the existence of an upward current, under 

 the circumstances described in the commencement of this paper. 



They moreover yield a series of results which he hopes the Society 

 will deem to be not without interest. 



These results show it to be probable, if not certain, that the ordi- 

 nary temperature of air within tubes, under the circumstances in 

 which these were placed, is higher than of that external to them, all 

 other relations of the tubes and surrounding objects being the same ; 

 they also show that in eight instances, when the thermometers in- 

 dicated an equality of temperature, within and external to the tube, 

 the rotations of the discs still continued ; and that when four coils 

 of tape, moistened with water, were applied round the external sur- 

 face of the tube, the rotations of the disc did not wholly cease. 



They also show, that when the atmosphere of the room, in which 

 the tubes were immersed, contained a larger or smaller proportion of 

 aqueous vapour, all other things being equal, the discs revolved with 

 more or less velocity ; but that when the atmosphere was deprived 

 in a great degree of aqueous vapour by the presence of quicklime, 

 the thermometric state in all other respects remaining the same, the 

 revolutions of the discs ceased. 



Adverting to the indications cited above, of a minute excess of 

 temperature in the interior of the tubes, and assuming that even 

 that slight excess would be sufficient to rotate the discs, still the 

 rotations diminished or ceased in proportion as the aqueous vapour 

 was withdrawn. 



Any increase of temperature which might have been produced by 

 the quicklime would have had a tendency rather to increase than 

 diminish the revolutions of the discs, but we have seen that the 

 abstraction of the vapour entirely arrested their rotation. 



With regard to the specific influence of each of the circumstances 

 and agents most probably concerned in producing the phenomena 

 described above, such as protection of the air within the tube from 

 lateral expansion and mechanical agitations, to which the external 

 air is exposed ; gaseous diffusion ; the unequal specific gravity of 

 air and vapour; and the subtle operations of temperature at all 

 times, the author is fully conscious that he has not ascertained their 

 respective values. 



