PROCEEDINGS 
OF 
THE ROYAL IRISH ACADEMY, 
1840. No. 22. 
April 13. 
SIR Wa. R. HAMILTON, LL.D., President, in the Chair. 
Samuel Hanna, M. D., William Torrens M‘Cullagh, Esq., 
George M‘Dowell, Esq., F.T.C., John Ball, Esq., Rev. 
Dr. Traill, Robert Alexander Wallace, Esq., and Thomas 
Newenham, Esq., were elected Members of the Academy. 
Dr. Apjohn, on the part of Surgeon Grimshaw, drew the 
attention of the Academy to a modification of the air-ther- 
mometer recently devised by the latter gentleman. The 
well-known objection to the ordinary air-thermometer he 
stated to be, that the air within the ball being in communica- 
tion (through the interposed column of fluid) with the external 
air, its volume comes to be affected not merely by changes 
in the temperature of the surrounding medium, but by the 
perpetually occurring variations in the atmospheric pres- 
sure. In fact, to render its indications truly thermometric, 
they must be reduced by calculation to a constant pressure, 
reference being made in every observation to a correct ba- 
rometer. Nor did Sir John Leslie, in his differential thermo- 
meter, get rid of this difficulty. It is true that all con- 
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