Geological Society of London. 141 



from the Forniche Kopf near Andernach down to within lOO feet of the present 

 Rhine. He thought, therefore, that the Rhine began to cut back a channel by- 

 rapids and waterfalls from the Rolandseck end at the first appearance of the land 

 above the Miocene sea, and before the close of the earth-movements and volcanic 

 eruptions, which seem to be connected with the later Miocene, but that it took the 

 river so long to eat its way back as far as Bingen that it had time to wind about 

 and form a broad valley in the upper part of its course, that the river continued to 

 run at the higher level at the Bingen end until, at comparatively a far less remote 

 period, the gorge was eaten back through this flat valley ; and when once the river 

 had got through the harder rocks near Bingen, it soon disposed of the softer beds 

 in the Mayence basin. 



Mr. Koch was inclined to think that tlie Jura chain had existence in Miocene 

 times, as beds of that age lay horizontally in hollows in the Jurassic rocks. He 

 quite agreed with Prof. Ramsay as to the terraces along the sides of the Rhine 

 gorge. 



Mr. Tiddeman did not see the difficulties suggested by Prof. Hughes. 



The President remarked that if the physical history of the Rhine were established, 

 it would throw much light on that of other great rivers. He considered the paper 

 of great value, but suggested a doubt whether the history assigned would account 

 for all the phenomena exhibited along the course of the river. There appeared to 

 have been at the commencement of the existence of the river several upheavals of 

 the land, but subsequent to the main upheaval of the Alps. He regarded the 

 channel of the river as entirely due to fluviatile action, but he confessed to having 

 some doubt whether the erosion of the river alone could have effected the enormous 

 amount of denudation exhibited in the district. He inquired whether there was 

 not a possibility of some marhie denuding power also having been at work. He 

 also inquired as to the flexure of the rocks and subterranean movements affecting 

 the conditions of the case, especially in connexion with the angles at which the 

 Miocene strata are tilted. A third question alluded to by Prof. Hughes was as to 

 the volcanic action that had gone on in the valley of the Rhine ; and he wished to 

 know whether that might not also have conduced towards the present contour of 

 the valley. As to the terraces, he accepted the author's view as correct ; but the 

 question still remained as to how far the gorge was due to gradual erosion or to 

 some subterranean action. 



Prof Ramsay, in reply to Mr. Hugh Miller, stated that the detritus brought 

 from the north was found in Switzerland, and that Prof Sandberger, as he had 

 found out since writing the paper, considered that at the time of its transport the 

 Jura was not in existence. He had conversed with all the principal Swiss geolo- 

 gists ; and it was from them he learnt that along what was now a part of the valley 

 of the Rhine a river flowing southwards during episodes in the Miocene period 

 carried pebbles from the north along its course. This river must have dated back 

 even to Eocene times. In reply to Prof. Hughes, he stated that the attribution of 

 the volcanic outflows to Miocene times was very problematical, and that there was 

 great probability of their belonging to a more recent period. Neither did they affect 

 the district mainly under consideration. There was no great successioii of terraces, 

 but one main terrace of fluvatile origin, of which extensive traces remained. 

 Similar terraces occurred on the Moselle. In reply to the President, he stated 

 that he did not think that volcanic action had anything to do with the formation of 

 the gorge. The Miocene strata lay in an approximately horizontal direction, and 

 were not tilted in such a manner as to suggest that their absence in the basin was 

 due to any disturbance of the strata. They must, in his view, have been of 

 necessity scooped away by the action of flowing water. 



2. " On the Correspondence between some Areas of Apparent 

 Upheaval and the Tbickening of Subjacent Beds." By W. Topley, 

 Esq., F.G.S., Geological Survey of England. 



The author referred to many instances in which beds have unequal development, 

 being much thicker in some places than in others; and the main object of his 

 paper was to show that such thickening and thinning of beds has an important 

 effect in producing the apparent dip of overlying beds. The thinning of any one 

 bed may have an appreciable effect in producing or increasing its own apparent 

 dip ; but where a whole series of beds thin constantly in one direction, the amount 



