[ 63 ] 



X. Proceedings of Learned Societies. 



EOYAL SOCIETY. 

 [Continued from vol. ii. p. 468.] 



April 27, 1876.— Dr. J. Dalton Hooker, C.B., President, in the 



Chair. 

 rpiIE Bakcrian Lecturo, "On the Gaseous State of Matter," was 

 -*- delivered by Prof. T. Andrews, LL.D., F.R.S., Yice-President of 

 Queen's College, Belfast. 



After referring to certain modifications in his former method of 

 working at high pressures, the author describes some preliminary 

 experiments which were undertaken to determine the change of 

 capacity in the capillary bore of the glass tubes under the pressures 

 employed. Prom these experiments it appears that, on raising the 

 pressure from 5 to 110 atmospheres, the capacity was increased for 

 each atmosphere by only 0*0000036, and that this change of capacity 

 was chiefly clue to compression of the internal walls of the glass 

 tube. Another set of experiments was made to ascertain whether 

 air or carbonic-acid gas is absorbed at high pressures to any appreci- 

 able extent by mercury. Por the method of operating and other 

 details reference must be made to the original memoir; but the 

 general result is that no absorption whatever takes place, even 

 at pressures of 50 or 100 atmospheres. The pressures are given 

 according to the indications of the air-manometer in the absence 

 of sufficient data (which the author hopes will be soon supplied) 

 for reducing them to true pressures. In the mean time it is pro- 

 bable, from the experiments of Cailletet, that the indications of the 

 air-manometer are almost exact at 200 atmospheres, and for lower 

 pressures do not in any case deviate more than -^ from the true 

 amount. 



In a note which, was published last year in the ' Proceedings ' of 

 the Society (No. 163), it was stated that the coefficient of expansion 

 (a) for heat under constant pressure changes in value both with the 

 pressure and with the temperature. The experiments on this sub- 

 ject are now completed, and are described at length in this paper. 

 The final results will be found in the two following Tables. In 

 the first Table the values of a are referred to a unit volume at 0° 

 and under one atmosphere. In the first column the pressure p 

 in atmospheres is in terms of the air-manometer. 



p. 



« (0°-7°-5). 



« (0°-64°). 



« (G4°-100°). 



17-09 





0-005136 



0-004747 



20-10 



0-00607 



0-005533 



0-004958 



22-26 





0-005811 



0-005223 



21-81 



0-00700 



0-006201 



0-005435 



27-69 



0-00782 



0-006737 



0-005730 



31-06 



0-00895 



0-007429 



0-006169 



31-49 



0-01097 



0-008450 



0-006574 



