TRANSACTIONS OF SECTION C. 060 



more quickly conducting material, and the more acid, specifically lighter, more 

 slowly conductinf- continental masses. The former are, in consequence of their 

 character and composition, the more stable portions of the resolidified crust. 

 Further, cooling therefore leads to their sinking down on the cooling and shrink- 

 ing nucleus, and their elbowing aside of the continental masses, which come to 

 be elevated in lines parallel to and extending along their margins. With further 

 cooling the superficial layers of the continents are thrown into folds and over- 

 folds, which would tend to find relief along the ocean margins and the central 

 axis of the Old World by over-thrusting of these layers. Central uplifts in the 

 continental areas may also have resulted from such pressure. 



The tendency of the ocean to become deeper and the continent to become 

 more elevated as time goes on, leads more and more to the withdrawal of the 

 waters of the ocean (which might at first almost or altogether have covered the 

 continental areas) from these areas, and hence to greater and greater restriction 

 in the limits of the areas of deposit as traced i'rom earlier to later gjological 

 times. 



The origins of the Mediterranean and of the central axis of the Old World 

 are directly deduced from theory, and the unequal distribution of land and sea 

 in the northern and southern hemispheres is also brought into line with it. 



Though the contraction of the ocean basins has been the main cause of the 

 deformation of the crust, the contraction of the continental areas has also had 

 some share in the result. The central ridge of the Atlantic bottom may be an 

 earth fold caused by pressure of the contiguous continental masses ; but it may 

 also be due to longitudinal fissures permitting volcanic action and consequent 

 accumulation of volcanic products, the fissures in such case marking the relief 

 of tension arising from the same cause. 



The formation of secondary ridges parallel to the oceano-contlnental margins 

 but at some distance towards the continental side, seems to have played an im- - 

 portant part in the evolution. Extending oceanwards in their operation thej'- 

 appear in some instances to have raised up portions of the ocean bottom into 

 continuity with the land surface. In this way, with the aid of volcanic action, 

 the ocean basins appear, in not a few instances, to have been successfully bridged. 

 As the permanency of the master-features of the globe in much their present 

 form is a necessary corollary of the theory, such bridging of the ocean basins 

 also becomes a necessary part of the theory, and is fairly met on the lines 

 indicated. 



Explaining as it does the general outlines of continents and ocean basins, as 

 ■well as a large number of facts both in geography and geology, it is contended 

 that the theory as sketched does represent in a general way the actual process by 

 which the permanent features; of the globe took origin. 



WEDXESDAY, SEPTEMBER 16. 

 The following Report and Papers were read :— 



1. Bepovt of the Committee on Chanc/es in the Sea Coast of the United 

 Kingdom. — See Reports, p. 258. 



2. Notes on the Sarsen Stones of the Bagshot District. 

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



The blocks of sandstone or quartzite known as Sarsen Stones are found in 

 many parts of the soutli of England. They occur at or near the surface of the 

 ground, as well as in or at the bottom of the gravels. They. are usually believed 

 to he derived from the Bagshot or Reading Reds, but there does not seem to be 

 definite evidence of the discovery of a Sarsen Stone in situ in these or in any 

 other formation. 



