542 J. Lomm — The CrystaUine Gneisses. 



believe that Anglesey kept its head above water during the Meco- 

 zoic and Cainozoic Periods, it follows that portions of the Archaean 

 rocks on the north-west of the island have never been submerged 

 at all. 



A second aggregation of shorelines is seen in the Midlands, closely 

 following the Archfean ridge. This is not so striking an example 

 as that in Anglesey, but it is sufficient to suggest that the solid 

 cores of the primitive wrinkles have resisted great lateral ci'ushings, 

 while the sedimentary rocks deposited in the troughs have been 

 crushed, folded, and cleaved to a great degree. We might almost 

 compare the ridges to nodes in the great wave-like motions which, 

 have swayed the surface rocks up and down like long ocean swells. 



In order to bring the arguments given above into better view, 

 I may summarize the chief points touched upon. 



1. The worldwide distribution of the fundamental gneisses and 

 schists and their uniformity of characters suggest a cause whicb 

 affected the world as a whole. 



2. Professor Darwin has shown, altogether apart from geological 

 reasoning, that primitive wrinkles would be formed on the crust 

 by the action of the moon when nearer the earth. So far as I have 

 been able to gather, the ridges formed by the oldest rocks now 

 existing correspond in direction with the wrinkles Professor Darwin 

 describes. 



3. The lithological characters of the primitive rocks are such as 

 would result from the flowing and shearing of rocks (in which 

 crystals had already formed but were in a highly heated condition), 

 on being raised into wrinkles by differential movements. 



4. The earliest sedimentary rocks were deposited in long troughs, 

 parallel to each other for the same latitude. 



5. The ridges themselves never unfolded. Some of them have 

 remained at approximately the same level through all time, and 

 others have partaken of greater movements in later times. The 

 continuity of the ridges has been destroyed in some places by later 

 foldings not parallel to themselves. 



And now, in conclusion, may I refer to a matter which arises 

 directly out of the subject-matter of the Address ? In many text- 

 books, and even in geological papers, the young student is told in 

 effect that "every part of the earth has been raised and depressed 

 times without number." As our knowledge increases I believe that 

 this loose and offhand method of dealing with earth-movements will 

 give place to more precise and definite statements. It will then be 

 found that changes of level have not taken place promiscuously, but 

 according to certain laws, of which we have at present only the 

 foreshadowing. I do not refer so much in this matter to local 

 movements, which can be traced to obvious local causes, but rather 

 to those extending over great areas. A large movement must have 

 a deep-seated cause, which will leave permanent witness to its 

 operation. 



