Geological Society, 659 



So far we have verified the first two of these results, as far 

 as we are at present able to interpret our work. We found 

 the absorption coefficients of the cathode rays produced in 

 gold by Se X-rays to be in air at atmospheric pressure 

 26*2 cm. -1 , and in ethyl bromide of equal density 24*5. The 

 absorption coefficients of the Mo X-rays were 16*3 in air and 

 29*2 in the ethyl bromide. It may seem paradoxical that the 

 faster Mo cathode rays should actually have a higher ab- 

 sorption coefficient in ethyl bromide than the slower Se 

 cathode rays ; but, again, it is to be remembered that ab- 

 sorption coefficients represent an average of conditions. 



We have also found a deficiency in the ionizing power of 

 the Mo X-rays acting on ethyl bromide. But we are not 

 satisfied with measurements which depend on cathode-ray 

 streams of somewhat doubtful composition, and are about to 

 use cathode rays of known speed. I may add that we are 

 also substituting another metal for the gold leaves, because 

 it seems very probable from Mr. Chapman's proof of the 

 identity of the homogeneous radiations from Au and Br that 

 we have been prejudicing our own case. 



These results indicate that Lenard's rule, viz., that the 

 penetration of cathode rays depends only on the density of 

 the matter penetrated is not universal, which, after all, might 

 be expected. When Mr. Chapman says that there is no ex- 

 perimental evidence whatever of its violation in any case, he 

 cannot have noticed a reference to these results iu an address 

 which I gave at Dundee last September. 



As I have said above, we hope to carry out all three of the 

 tests I have mentioned. W. H. Bragg. 



LXV. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 200.] 



November 20th, 1912. — Dr. Aubrey Strahan, F.R.S., President, 



in the Chair. 



rPHE following communications were read : — 



-*- 1. ' On the Hafslo Lake and the Solvorn Valley (Norway).' 



By Horace "Woollaston Monckton, Treas.L.S., F.G.S. 



The district dealt with lies north of the main Sogne Fjord and 

 west of the Lyster Fjord. Attention is drawn to a series of valleys 

 running from the area of. the Jostedal snowfleld and cutting the belt 

 of Silurian rocks which crosses the district in a north-easterly and 

 south-westerly direction, and to a second series of valleys which run 

 parallel to the snowfleld and to the Silurian belt. The author 



