IIS PEOF. J. LOGAN LOBLEY, F.G.S., F.E.G.S., ON 



have been a difference in the effect of attraction of the moon's mass 

 which would have affected powerfully the tides ; and supposing at a 

 certain period, say the Jurassic or the Old Eed Sandstone period, 

 the moon was only one-half the distance from the earth that it is 

 now, the effect of the attraction of our satellite would have been 

 probably quadrupled to what it is at the present day. What would 

 be the effect of that on the tides The tides would rise and fall 

 ■enormously to a greater extent than they do at the present day, 

 and the result of that rise of the tides would be to produce an 

 amount of denudation and erosion of the rocks vastly greater than 

 is now the case. If the waters rose, say, four times higher along the 

 coasts at that period than they do now, so the period of oscillation 

 would have to take place in the same period, or as nearly so as 

 possible, and the effect of that upon the land would have been 

 vastly greater than it is at the present day.* This view was 

 many years ago suggested by Sir Kobert Ball, and it imprinted 

 itself upon my mind as a phenomenon that has to be taken into 

 consideration when we speak of the uniformity of these natural 

 agencies of denudation and erosion in past geological times as 

 compared with that of the present day. 



Professor Lobley. — I must express my thanks for the kind 

 attention given to my paper, and so many points have been raised 

 I am afraid that I should have to take up as much time as it took 

 to read it to reply to them ; but there are two or three points that 

 have been put saliently. 



With regard to Professor Hull's remarks about the amount of 

 •denudation, and the amount of destruction of the rocks. Professor 

 Hull is a high authority, and I would pass that over. My estimates 

 were round numbers and figures just to illustrate the point that 

 a very large amount of the stratified and other rocks had been 

 denuded away. I agree that some of the higher mountain regions 

 -of Scotland and Wales were above the sea during Jurassic times. 

 I do not measure the amount of material which had been removed 

 from either area. 



The geological map shows that a very large proportion of the 

 formations that have been there originally have been removed and 



* On the su])positioii that the diurnal rotation of the earth was what 



.it \» DOW. 



