750 
professor o. Reynolds on certain dimensional 
imply that the plates were so thick that the conduction of heat through the plate 
produced no appreciable effect on the temperature of the surfaces of the meerschaum. 
It appeared, however, from subsequent experiments that in all probability there was a 
small difference in the two instruments. The original instrument, that in which the 
experiments on plate No. 2 were made, had been used a great deal, and the surfaces 
of the tin plates which were opposite to the meerschaum had lost all their polish and 
become black, while in the second instrument the plates were new and bright. It 
might, therefore, be expected that the old plates would radiate more heat than the 
bright plates, and so better maintain the difference of temperature, and besides this 
the india-rubber rings in the new instrument were somewhat thicker than those in the 
old one, and so the space between the plates and the surface of the meerschaum was 
greater than in the old instrument. It appears, therefore, that these causes may have 
neutralised the increase in the difference of temperature that would otherwise have 
resulted from the extra thickness of the plate. And it will be seen that this conclu¬ 
sion was confirmed when on introducing a new stucco plate into the old instrument 
new tin plates and thicker rings were also introduced. 
ft 
Infusion of air. 
The curves, fig. 5, show the degree of regularity attained in these experiments. 
Such discrepancies as there are, are apparently owing to the absorption and exhalation 
of the gas by the india-rubber and possibly by the plate itself, for these discrepancies 
only occur at the lower pressures. 
Fig. 5. 
In the case of hydrogen the greatest care was taken to get the gas pure; but it is 
not to be supposed that as the gas was pumped out the residual gas would maintain a 
