Geological Society. 247 



Summary. 



1. The Balmer series is produced when positively charged 

 hydrogen atoms pass through hydrogen as positive rays. 



2. The second spectrum is produced when positively 

 charged hydrogen molecules pass through hydrogen as posi- 

 tive rays. 



3. Stark and Wilson's failure to find the Doppler effect 

 for the second spectrum of hydrogen is probably to be 

 explained by there being no molecules in the positive rays 

 they used. 



4. In certain circumstances a great change can be made 

 in the nature of the positive rays given by a discharge tube 

 by subjecting it to a magnetic field. 



In conclusion, I wish to express my sincere thanks to my 

 father, Sir J. J. Thomson, for his interest and advice during 

 the progress of the work described above. 



XXVIII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxxix. p. 699. j 



December 17th, 1919.— Mr. G. W. Lamplugh, F.E.8., President, 

 in the Chair. 



r PHE following communication was read: — 



' A Rift- Valley in Western Persia.' By Prof. S. James Shand, 

 D.Sc, F.G.S. 



Asmari Mountain, near the oilfields of Maidan-i-Naftun, in the 

 Bakhtiari country of Western Persia, is an inlier of Oligocene 

 limestone among the beds of the Fars Sj^stem (Miocene), the 

 latter consisting, in the lower part, of bedded gypsum with inter- 

 calated shales and a few thin limestones. The mountain is a 

 Avhale-back, 16 miles long and 3 miles wide at the middle, formed 

 by a simple symmetrical anticline plunging at both ends. The 

 north-western end plunges rather steeply, and shows no abnormal 

 structures ; but at the south-eastern end the fold has collapsed 

 along its length for a distance of 3 miles, letting the gypsum-beds 

 down into a trough in the limestone. 



This trough is bounded by two main faults hading north-eastwards 

 and south-westwards respectively, with an average hade of 20°, and 

 marked by steep escarpments. The northern scarp, which lies 

 practically along the axis of the anticline, is at one point 500 feet 

 high; but the southern one, being low down on the flank of the 



