26 



Anniversary Meeting. 



[Nov. 30, 



with what is known in the case of solids, that in gaseous media also there 

 is equality in the powers of radiation and absorption. Bodies which exert 

 an absorbent effect in the liquid form preserve it in the gaseous state. If 

 further experiments should confirm Prof. Tyndall's views upon the absorp- 

 tive action of aqueous vapour upon radiant heat of low intensity, these 

 results must materially modify some of the views hitherto held upon the 

 meteorological relations of aqueous vapour. 



The Bakerian Lecture, by Mr. Sorby, is entitled by him " On the Direct 

 Correlation of Mechanical and Chemical Forces." In this paper are em- 

 bodied a series of observations upon the influence of pressure upon the 

 solubility of salts, in which he has obtained results analogous to the changes 

 observed in the freezing-point of liquids under pressure. He finds, in cases 

 where, as is usual, the volume of the water and the salt is less than the 

 volume of the water and the salt separately, that the solubility is increased 

 by pressure, but that, in cases where (as when sal-ammoniac is dissolved in 

 water) the bulk of the solution is greater than that of the water and salt 

 taken separately, the solubility is lessened by a small but measurable 

 amount. On the contrary, salts which expand in crystallizing from solu- 

 tion must, under pressure, overcome mechanical resistance in that change ; 

 and as this resistance is opposed to the force of crystalhzation, the salt is 

 rendered more soluble. The extent of the influence of pressure, and the 

 mechanical value of the force of crystalline polarity, were found to vary in 

 different salts. Mr. Sorby also indicates the results of the action of salts 

 upon certain carbonates under pressure, and purposes pursuing his re- 

 searches upon chemical action under pressure. This paper may therefore 

 be regarded as the first of a series upon a highly interesting and important 

 branch of investigation, for which Mr. Sorby appears to be specially fitted, 

 from his combining the needful geological knowledge with the skill in 

 manipulation required in the physical and chemical part of the inquiry. 



The examination of the bright lines in the spectra of electric discharges 

 passing through various gases, and between electrodes of various metals, 

 has of late years attracted very general attention. Each elementary gas 

 and each metal shows certain well-marked characteristic lines, from the 

 presence or absence of which it is commouly assumed that the presence or 

 absence of the element in question may be inferred. But the question 

 may fairly be asked. Has it been established that these lines depend so 

 absolutely on chemical character that none of them can be common to two 

 or more different bodies ? Has it been ascertained that, while the chemical 

 nature of the bodies remains unchanged, the Hnes never vary if the circum- 

 stances of mass, density, &c. are changed ? What evidence have we that 

 spectra are superposed, so that we observe the full sum of the spectra 

 which the electrodes and the medium would produce separately ? 



To examine these and similar questions in the only unimpeachable way 



