On the Shelves of Lochaher. 3 



shock necessary for sueli a separation would have effec- 

 tually disturbed, if not obliterated, the parallel shelves. 

 How Mr Darwin could adopt such an idea, after affirming 

 that no sudden change could have taken place, I am at a loss 

 to understand. 



Mr Miluo's theory requires a more detailed examination ; 

 and, fully sensible of this, I went to Lochaber shortly after 

 his paper was read before the Royal Society of Edinburgh ; 

 and while I found a confirmation of the objections that had 

 occurred, I met with nothing which did not appear to con- 

 firm my own views. I am not, however, so unphilosophically 

 wedded to them as to imagine they will withstand the as- 

 saults which the observation of others may enable them to 

 make on them. At all events, the time has not yet come for 

 the final settlement of any physico-geological question. 



]Mr Milne goes back to a period long antecedent to the 

 formation of the shelves, in order to pave the way for them ; 

 and if I have not rightly understood him, the fault must rest 

 Avith me ; for, both in conversation and correspondence, he 

 has, with the greatest readiness, answered every question. 

 He has, too, materially helped in the construction of the map, 

 so that by its assistace both of us may be better understood 

 than vve would have been without it. 



Mr Milne assumes — 



1. That our island had been submerged in the ocean, where 

 it acquired its present aspect. 



2. That during the period of submergence, the hollows be- 

 tween the mountains were filled Avith boulder clay, gravel, 

 sand, mud, &c. 



3. That after the hollows were filled the land began to rise. 

 These three conditions are preliminary to the action by 



which the existence of the shelves is attempted to be ex- 

 plained. They involve some important considerations, ren- 

 dering some special hypothesis necessary for their explana- 

 tion. We may pass over the first assumption ; but the 

 second seems to require some consideration before it can be 

 admitted as a postulate. The hollows between the moun- 

 tains are all filled up ; and the mass of loose matter employ- 

 ed for that pui'pose is far too great for being collected by any 



