472 



NA TURB 



[April 1 6, 1874 



valley from early times to the present day. For many years I 

 had an ambition to work out the history of the Rhine. I have 

 known it now for more than hventy years ; going often up and 

 down the river, and sometimes for weeks — once for months — 

 living on its banks. For the last thirteen years, unfortunately, I 

 never was able to return to it, but the problem I had marked 

 out for myself remained in my mind, and last year I went, and 

 worked it out, with the result which is now to be explained. 



First, with regard to the great main features of the Rhine 

 valley ; it has its sources, as every one knows, in the mountain 

 regions of Switzerland, one of which is in the valley of the Vor- 

 der Rhine, and the other in that of the Hinter Rhine, both glacier 

 regions. The ground where it rises isfrom 7,000 to 8,ooofeet above 

 the level of the sea. From thence it passes to the Lake of Con- 

 stance, 1,305 feet above thesea ; and beyond, in a westerly direc- 

 tion, by .Schaffliaussen to Basel, where, at the bridge, the level of 

 the water has an average height of about 803 feet above the sea. 

 Thence it flows down the great upper plain of the Rhine northerly 

 between the .Schwartzwald and the Vosges to Mainz, where the 

 height of the river is about 531 feet above the level of the sea, thus 

 showing a fall between Basel and Mainz of about 272 feet, which 

 gives an average slope for the running of the river of about 

 3 ft. I J in. per mile. Beyond that, proceeding to the north, we 

 come to the deep gorge of the Rhine, passing between liigh 

 cliffy banks, which begin at Bingen and continue down to 

 Rheineck in the neighbourhood of the Siebengebirge, for 

 a distance of from 60 to 70 miles, according as you 

 take into account all the windings or omit them. Beyond the 

 Siebengebirge tliere is a plain, partly formed of the delta of the 

 river, which gradually merges into the great fiats that extend all 

 the way from Calais to the Elbe. 



Now the main question I have to bring before you is, first, 

 what is the origin of the great upper plain that lies between 

 Basel and Mainz ? and, secondly, what is the origin of the gorge 

 between Mainz and Rheineck ? Why are they there, and by 

 what means have this plain and this gorge assumed their present 

 forms ? 



When you stand above Bingen, or, better still, ifyou ascend the 

 Taunus and look southerly, and consider the narrowness of the gorge 

 and the great hilly barrier of rock that must once have extended at 

 Bingen across the lower end of the plain, the impression is irre- 

 sistibly conveyed to the mind that before that gorge was opened 

 a vast lake must have reached all the way from tliat barrier to 

 where Basel now stands, covering the great plain that lies between 

 the mountains of the Vosges and those of the Schwartzwald. 

 And so thorouglily has this idea taken possession of the popular 

 mind, at least of those who have at all considered the subject, 

 that we find this statement made in some of the Guide Books of 

 the time, and notably by Baedeker, where it is stated that a 

 lake must have covered the whole of that vast plain, 1 70 miles in 

 length, at a comparatively recent period. It is a very obvious 

 theory and has much to recommend it, for it seems so clear that, 

 before tlie gorge was opened, all that plain must have been 

 covered with a sheet of water, and it is hard to realise 

 that such has not been the fact. When I first entered on the sub- 

 ject I was impressed with this idea, and I began to cast about 

 and endeavour to find a reason for the scooping out of the gorge, 

 and for the consequent drainage of the supposed lake. 



Having years before written a paper on the origin of 

 the lake basins of Switzerland, North America, and other 

 parts of the world, and having attributed the formation of 

 many of these, but by no means all of them, to the action of 

 glacier-ice during the glacial period, my first impression was that 

 ice might have had at least something to do with tlie scooping 

 out of the great valley that lies between the north flanks of the 

 Jura, the Scliwartzwald, the Vosges, and the Taunus. But 

 while slowly passing up tlie river, and searching for proofs 

 which might either confirm or contradict this view, I was 

 soon obliged to give up the idea that glacier-ice had anything 

 to do with scooping out the great hollow. For on one side — 

 that of the mountains of the Schwartzwald — I found that none 

 of the glaciers of that region (and there are proofs that glaciers 

 once existed there) even extended well down into the valley of 

 the Rhine. And on the opposite side of the Rhine Valley, that 

 of the old glacier region o( the Vosges, I found no proof that 

 they ever extended down so far as the plain. There is 

 also no proof that the glacieis of the great glacial epoch of 

 Switzerland ever extended as far north as Basel. Neitlier are 

 there any signs of erratic blocks or other kinds of moraine mat- 

 ter on the pl.ains or hill-slopes about Bingen, which one miglit 

 expect to find there had the whole of the great plain of the 



Upper Rhine been once filled with glacier-ice. Therefore this 

 theory, which I had not definitely formed, but which I sur- 

 mised might possibly have had something to do with the subject, 

 entirely melted away, and other hypothetical views along with 

 them, and I was obliged to begin anew. 



Accordingly I vent to Switzerland, and with the help of 

 friendly Swiss geologists, examined part of the Miocene or Middle 

 Tertiary rocks between the Oberland and the Jura. 



To make tlie rest of the subject clear, I must now say 

 a few words about the origin of mountain chains. Most 

 people are familiar with the outlines of the nebular hypothesis. 

 1 he whole solar system was once in a nebulous state, and as 

 this nebulous mass revolved in space, portions of it were thrown 

 off, and one of these consisted of the matter which, by and by, 

 resolved itself into the present earth. This nebulous fluid, in 

 virtue of gravity, by degrees condensed more and more, and, 

 passing through what we may call the molten state, in the course 

 of time began to assume a solid form, and a hard outer crust 

 was at length produced which enclosed a highly-heated fluid 

 mass within. This crust, which continued to thicken in conse- 

 quence of radiation of heat, because of the law of gravitation, 

 was ever drawn towards the centre of the eaith. By this process 

 the circumference of the earth necessarily became less, and that 

 consolidated rocky sphere which fotmed the outer shell of the 

 earth was forced to readjust itself so as to occupy a diminishing 

 area. Thus it happened that while some parts sank, other 

 parts of the crust were crumpled, and relatively raised higher 

 than other portions of the crust that still retained their original 

 curves as part of a sphere. 



This hypothesis, which, as far as I know, was first propounded 

 by Elie de Beaumont, may be looked upon as the origin of 

 mountain chains. What began in the earlier and prehistoric 

 times of geological history, seems to have been going on steadily 

 down to the present day, and thus it happens, that geolo- 

 gists can prove mountain chains to be of verj' different ages, and 

 that, of whatever age they may chance to be, the strata that com. 

 pose them are found to be bent and contorted. Tliis contor- 

 tion of strata took place simply from that shrinking of the 

 earth's crust w'hich was the natural result of radiation of heat 

 into outer space. Portions of the crust more or less gave way to 

 lateral pressure, wdiile other parts of the great sph.eroidal curve 

 more or less retained what we call horizontal or nearly horizon- 

 tal position. 



In this way it happened that at a certain period of geological 

 history which preceded the formation of the Miocene rocks in 

 the region now occupied by the Alps, a disturbance of the 

 earth's crust took pLicc, due to shrinkage of the general mass, of 

 such a nature that the Alpine strata were thrown into highly- 

 contorted fonns, and a great mountain range of pre- Miocene age 

 was the result. On the north of these mountains the Miocene 

 strata began to accumulate in great lakes. But these lakes lay 

 so near the level of the sea, that every now and then, by 

 depression of the land, they sometimes sank a little below the sea, 

 and the sea invaded the area formerly occupied by fresh water. 

 The result was that in Switzerland, between the Oberland and 

 the Jura, and much farther north, the Miocene strita which are 

 hundreds and sometimes thousands of feet thick, are now found 

 to consist of interstratifications of marine, brackish, and of fresh- 

 water beds. At that time the Jura had no existence. It is the 

 result of a later disturbance of the crust of the earlh, and thus it 

 happened that all the Miocene w.aters in which were de- 

 posited the strata that now lie between the Obe-lind and 

 the Jura originally spread northwards far across the area now 

 occupied by the Jura, and into the di trict of the present 

 plain of the Rhine between Basle and Bingen. 



It is hard to realise the scenery of that time ; but partly by 

 an effort of imagination, and partly by special knowledge of the 

 fossils contained in the rocks, it is possil^le to foim some con- 

 ception of the appearance ol the country. 



On the east and west of the great valley were rrounlainous 

 ranges now called the Schwartzwald and the Vosges, while far to the 

 south rose the high mountains of the pre-Miocene Alps, more 

 or less covered with a forest vegetation. On the banks of 

 the lakes there grew in an early stage of the Miocene epoch vast 

 numbers of forest-trees and evergreen shrulis, of genera such as 

 are now characteristic of tropical and sub tiopical countries ; 

 figs and vines, many species of Brotoacea; analogous to those that 

 still grow in the Australian continent, together with cypress, 

 sequoia, cinnamon, fan palms, and palmetioes, ferns, hornbeims, 

 and buckthorns, all of genera still familiar, but mostly if not alto- 

 gether of extinct species. At a later date this vegetation partly 



