228 A. C. RAMSAY ON THE PHYSICAL 



one continued, even, eminent ridge of land, not divided into parti- 

 cular mountains and hills by intervening valleys, as now it is, but 

 that after the rivers began to flow down from the top of it, by little 

 and little fretting and corroding the ground, they made valleys, and 

 daily more and more ; and by this means the whole Appenine came 

 to be divided into many hills and mountains." 



It is not, however, to insist on these simple principles, enlarged 

 by modern research, versus unnumbered unproved open faults, frac- 

 tures, and tumultuous splittings of mountains, that this paper has 

 been prepared ; but having already written on the physical history 

 of rivers both foreign and British, the details of which, comparatively 

 simple, only grew on my mind by slow degrees, I have at length 

 fallen on the Dee as an example of one of many rivers, the history 

 of which is much more complicated than, for example, that of the 

 Po, the Rhine, the Severn, or the Thames ; and I hope I have 

 succeeded in unravelling that history. If so, the Dee, as a living 

 river, has a history compared with which those of the Thames, the 

 Rhine, the Ganges, and many other great rivers of the modern 

 world are matters of yesterday. 



Discussion. 



Mr. Thorpe stated that Arenig Lake, and not the Bala Lake, 

 was the source of the Dee, and wished to know what origin Prof. 

 Ramsay attributed to the former. 



Mr. Hicks considered that the author's explanation of the origin 

 of the lake and the gorge through which the Dee afterwards flows 

 was not a correct one, and that these hills were only elevated at the 

 close of the Palaeozoic period, and not, as maintained by the author, 

 in Silurian times. In a previous paper Prof. Ramsay claimed that 

 the Menai Straits had been excavated by a huge glacier moving 

 from N.E. to S.W. ; whilst in the present communication he attri- 

 buted Bala Lake to a glacier moving in exactly the opposite direc- 

 tion. Now, as the valley of the Dee and the basin of Bala Lake 

 are roughly parallel to the Menai Straits, they should have been 

 formed by the same glacier. Neither, however, is due to glacial 

 action ; but both are produced by two parallel faults that were 

 formed at the close of the Palaeozoic period. 



Prof. Seeley inquired what grounds there were for attributing 

 such an ancient date to the Dee. There was no proof that the Lias 

 had not formerly extended over this district. With regard to this 

 old tableland, which the author considered to have been formed in 

 pre-Carboniferous times, and subsequently covered by Carboniferous 

 strata, he thought it was impossible that these Carboniferous strata 

 could have been denuded and the old tableland left intact. The 

 water running off the land as it rose would form the first valley ; and 

 both would suffer together. 



Prof. Ramsay, in reply, stated that he considered Bala Lake to be 

 the commonly acknowledged source of the Dee. The Arenig lakes 

 were also due to glacial action. He had treated the disturbances of 



