160 Geological Society : — 



He also attempts to show that his third principle, " the conserva- 

 tion of energy," implies the continuity of the molecular rotations 

 across the interface ; but in his proof of this (p. 148) he omits, in 

 calculating the stresses, the terms involving the dilatation. Now 

 though this vanishes, its coefficient in the expression for the stress 

 is infinite, and the product of the two, as Green showed, must be 

 retained. 



A chapter at the end of the theoretical part is devoted to the 

 Electromagnetic theory of Light, and there is some confusion between 

 the periodic changes in the aether which constitute light, and those 

 to which electric and magnetic displacement are due. According to 

 Maxwell's theory, the electric displacement is normal to the plane 

 of polarization, the magnetic displacement is in that plane, and 

 both are in the wave-front ; but Maxwell nowhere states that the 

 displacement which constitutes light coincides with the electric or 

 magnetic displacement, and either view is open to his supporters. 



XXIY. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 78.] 



December 16, 1885. — W. Carruthers, Esq., Vice-President, 

 in the Chair. 



nPHE following communications were read : — 



-*- 1. " Old Sea-beaches at Teignmouth, Devon." By G. Wareing 



Ormerod, Esq., M.A., E.G.S. 



The author stated that while old records show that no important 

 changes have taken place in the level of the Teignmouth district 

 during the historical period, the excavations made in recent drainage- 

 operations in the present year showed the existence of at least two 

 series of beaches. The oldest sea-beach, which is a few feet above 

 the present sea-level, was partly washed away and then covered up 

 by later deposits exhibiting evidence, in a number of delicate bivalve 

 shells in an unbroken condition, of having been deposited in a calm 

 sea. 



2. " On the Gabbros, Dolerites, and Basalts of Tertiary Age in 

 Scotland and Ireland." By Prof. John W. Judd, F.B.S., Sec. G.S. 



In previous papers, published in 1874 and 1876, it has been 

 demonstrated by the author that there exist in Scotland and in 

 Hungary igneous rock-masses presenting the most perfectly crystal- 

 line characters and belonging to the Tertiary period. It was further 

 shown that such highly crystalline, plutonic rocks are seen passing 

 insensibly into volcanic rocks of the same chemical composition — 

 gabbros into basalts, diorites and quartz -diorites into andesites, and 

 quartz- andesites and granites into rhyolites — the lavas in turn gra- 

 duating into the perfectly vitreous types known as tachylytes and 

 obsidians. 



The present paper deals with the basic rocks of Western Scotland 



