Geological Society. 197 



is sufficient to enable a detailed study to be made of them. 

 The further account of these investigations and their extension 

 to other radioactive bodies is reserved for a later paper. 



In conclusion I desire to express my best thanks to 

 Prof. Rutherford for suggesting this research, and for his 

 kind interest and advice throughout the experiments. 



XXII. Notices respecting New Boohs. 



Lehrbuch der Thermochimie mid Thermodynamic. By Professor 

 Dr. Otto Sacktjk. Pp. viii + 340. Berlin: Julius Springer, 

 1912. Price 12 M. (13 M. bound). 



A VERY thoroughgoing treatise covering the whole of the subject 

 ^^ in a very excellent manner. Although it cannot claim any 

 originality except that of treatment, we cannot imagine a better 

 guide to the student than what it provides. We turn naturally 

 to the parts dealing with the newer conceptions, and find that it 

 does not lack even these. The third law of thermodynamics of 

 jNernst and the speculations of Einstein (based on Planck's law of 

 radiation) are very satisfactorily put forward. We recommend 

 the book most heartily. 



XXIII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxiv. p. 901.] 



April 17th, 1912.— Dr. Aubrey Strahan, F.K.S., President, 



in the Chair. 



rPHE following communications were read : — 



1, 'The Pre-Cambrian and Cambrian Rocks of Brawdy, Hays- 

 castle, and Brimaston (Pembrokeshire)/ By Herbert Henry 

 Thomas, M.A., B.Sc, Sec.Gr.S., and Prof. Owen Thomas Jones, 

 M.A., D.Sc, F.G.S. 



The district dealt with in this paper lies about 8 or 10 miles to 

 the east of St. Davids, and consists of pre-Cambrian plutonic and 

 volcanic rocks surrounded by, and intimately associated with, sedi- 

 mentary rocks of the Cambrian System. 



The pre-Cambrian igneous and pyroclastic rocks are brought to 

 the surface along an anticlinal axis which ranges in an east-north- 

 easterly and west- south-westerly direction: that is to say, approxi- 

 mately parallel to the ancient ridge of St. Davids. They are 



