292 Gfolugical Sucietij. 



a subject of regret, and well deserves the consideration of the 

 Council for the coming year. The Transactions of the Society 

 form unquestionably the most honourable official record of our la- 

 bours. It is through them that we are represented in the great re- 

 public of science ; and without them, beyond our own immediate 

 circle, we possess neitiier voice nor animation. 



The progress of our body in geological inquiry since the former 

 Anniversary, will be best understood by glancing over the various 

 memoirs which have been the subject of discussion at our meetings. 

 It will be useless to do this in the exact order in which they came 

 before us; I shall therefore follow that order in which the subjects 

 themselves appear to be naturally connected with each other. 



Our attention has been several times called to the theory of the 

 excavation of valleys, and to the elFects produced by river currents 

 in modifying the form of the solid parts of the earth. The subject 

 was introduced during the former year by a memoir of Messrs. 

 Lyell and Murchison, on certain portions of the volcanic regions 

 of Central France; in which they show (in accordance with the 

 views of Montlosier, Scrope, and some other writers) that the ex- 

 isting rivers have, by a long continued erosion, eaten out deep 

 gorges, not only through currents of basaltic lava which have 

 flowed through the existing valleys, but also through solid rocks 

 of subjacent gneiss. They further prove, on evidence which to 

 me seems not short of demonstration, that no great denuding wave 

 or mass of water lifted by supernatural force above its ordinary 

 level, could have assisted in forming such denudations : for the 

 country is still studded with domes of incoherent matter, the rem- 

 nants of former craters; from which ma)' be traced, continuously, 

 streams of lava, intersected in the courses of the rivers by these 

 deep gorges — the gages and tests of the erosive power of running 

 water during times comparatively recent. 



The elaborate Paper of Mr. Conybeare on the valley of the 

 Thames is still fresh in our recollection. He proves that the ero- 

 sive power of the river has, within the records of history, produced 

 no effect on the general features of the country through which it 

 flows, and that the propelling force of its waters is not now, and 

 never could have been, adequate to the transport of the boulders 

 which lie scattered on the sides and summits of the chains of hills 

 through which it has found a passage: that much of the waterworn 

 gravel, which has been drifted through the breaches opened in the 

 sinuous line of its channel, is composed of rocks not found within 

 the limits of its basin; and that the form of the country is often 

 the very reverse of that which would have been produced by mere 

 fluviatile erosion, however long continued. Similar facts are sup- 

 plied by nearly all the greater valleys of England ; and on the 

 whole they point to one conclusion, that fluviatile erosion, as a 

 mere solitarj' agent, lias produced but small effects in modifying 

 the prominent features of our island : at the same time they leave 

 untouched all the facts of an opposite kind, supported by direct 

 evidence, whether derived from the volcanic districts of Central 



Trance, 



