190 Prof. W. B. Morton on the Amount of Water in 



spheric is so much less than that at atmospheric tempera- 

 ture, that it seems doubtful whether the results would be 

 sufficiently definite to lead to any certain conclusion. 



8. It is not pretended that the experiments which I have 

 described are in any way final. My only object in under- 

 taking them was to compare the potassium rays with the 

 /3rays of uranium. The absorption of the former in solutions 

 is abnormal and so, it appears, is the absorption of the latter. 

 Moreover, the abnormalities are, in general, of the same 

 kind. The object of the investigation is attained, and it is 

 not proposed to pursue it further in the immediate future. 

 Light is far more likely to be thrown upon the difficult 

 question of the absorption of j3 rays by experiments, such as 

 those of McClelland, Schmidt, and Crowther, on the 

 secondary radiation excited, than by any direct measurements 

 of the absorption coefficient. 



I am much indebted to Mr. Crowther for valuable 

 suggestions and for the benefit of his great experience in 

 work of this nature. 



Summary. 



The absorption of the ft rays of uranium in liquids 

 (especially solutions) has been investigated. It is doubtful 

 whether liquids possess a true absorption coefficient defined 

 as a quantity occurring in an exponential equation. 



One of several possible, but inconsistent, methods of 

 estimating a quasi-absorption coefficient has been selected. 

 It appears that the relation between the values of \/p (where 

 A, is estimated by this method) for the solution, the solvent 

 and the solute is not linear. It is possible that the value 

 for a solution should be greater than either of the values for 

 the solvent or the solute, or should be less than either of 

 those values. 

 Sept. 3, 1908. 



XI. Note on the Amount of Water in a Cloud formed hy 

 Expansion of Moist Air. By "W. B. Morton, Professor of 

 Natural Philosophy, Queen's College, Belfast *. 



TT^HE calculation of the total mass of water condensed, 



X when a volume of air saturated with vapour receives a 



given sudden expansion, is an important step in Prof. J. J. 



'Thomson's determination of the charge on a gaseous ionf. 



* Communicated bv the Physical Society : read June 12, 1908. 

 f ' Conduction of Electricity through Gases/ p. 122. 



