PROCEEDINGS 



OF 



THE ROYAL IRISH ACADEMY. 



1840. No. 22, 



April 13. 



SIR Wm.R. HAMILTON, LL.D., President, in the Chair. 



Samuel Hanna, M. D., William Torrens M*Cullagh, Esq., 

 George McDowell, 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- 



2m 



