378 



NATURE 



[Mar. 14, 1872 



all trending south-east to north-west (or in the direc- 

 tion from the Alps), standing out, on the denuded high 

 plains, as monuments of its passage. M. Belgrand points 

 out that where the Tertiary strata have presented a resist- 

 ance which the waters could not overcome, the high-level 

 valleys formed by the diluvial waters are, in such cases, 

 fronted in the opposite range of hills, against which 

 the mass of waters impinged, by a deep bay cut by the cur- 

 rent in those hills, and that the waters thus checked in their 

 course were turned off at acute angles, until they reached 

 the main channel of the Seine, tending thereby to form 

 secondary or tributary valleys, which, when the deluge had 

 passed, contributed, with the Seine valley, to form the pre- 

 sent lines of river drainage. Such volumes of water as we 

 have depicted would, he argues, have swept the higher 

 channels and plains clear of debris, leaving the denuded 

 area covered merely with the silt thrown down from muddy 

 waters, and depositing the coarser debris in the middle 

 and lower range of the deeper channels through which the 

 present rivers afterwards took their course. In support of 

 this hypothesis, he shows that, whereas the basin of the 

 Seine is now drained by the one river and its tributaries, the 

 diluvial waters held their course straight across that basin 

 and debouched in five main channels — one, marked by the 

 hills of Montmorency and Satory, took the course of the 

 Seine below Montereau to the sea, but in a more direct and 

 broader line ; the second took the course shown by the 

 hills of Villers-Cotterets, thence across the present valley 

 of the Oise, along the valley of the Pays de Bray, to the sea 

 at Dieppe ; the third followed in part the course of the 

 Aisne, and then by the line of the Somme valley to the 

 sea ; and the fourth and fifth by those of the valleys of 

 the Aulthie and Cauche. M. Belgrand accounts for the 

 radidity and force of this cataclysm in the belief, which 

 he shares with M. Elie de Beaumont, that the elevation 

 of the Alps took place rapidly and suddenly. 



But there was a second elevation of the Alps, at a later 

 geological period, and which, according to M. Bel- 

 grand, may have produced a second deluge, not by 

 the displacement of the sea, for then there were only 

 lakes on the north-western side of those mountains, but by 

 the sudden melting of the snow on that great range ; 

 and our author again adopts the views of M. Elie de 

 Beaumont on this subject. This distinguished geologist 

 propounded in 1847 the theory that that last convulsion 

 of the Alps was accompanied by an enormous disengage- 

 ment of those gases to which has been attributed the for- 

 mation of the Dolomites and Gypsum beds of that chain^ 

 and that this caused the accumulated snows to melt in a 

 very brief period of time {iiii instant ). At the same time, 

 according to the same authority, the Pliocene lakes of 

 " La Bresse " were raised and drained. Thus, suggests 

 M. Belgrand, this second convulsion might have caused 

 another diluvial wave to pass over the basin of the Seine — 

 an hypothesis also advanced by M. Elie de Beaumont, who 

 speaks of "the probable concourse in this off-throw flood 

 {dt'vcrscmeut) towards the north-west, of the waters of 

 the great lake of La Bresse, in the production of the 

 diluvial phenomena observed in the neighbourhood of 

 Paris." 



We are disposed to agree with our author in the 

 opinion, which we have elsewhere expressed, that the 

 original contour of the surface with its higher valleys 



and hills, is due to a cause different from that which ex- 

 cavated the present river valleys— that it preceded and 

 is independent of it — but we cannot agree with him as to 

 the nature of that cause. Without going far into the 

 argument, we may mention that the well-known fact of 

 the gravel found in each tributary of the valley of the 

 Seine, consisting of the debris of those rocks only through 

 which that tributary flows, while in the Seine valley are 

 found the debris of all the tributaries, together with its 

 own and no more, is, it seems to us, a conclusive argu- 

 ment against the passage of a body of water from one 

 great basin to another — against the flow of such a body 

 of water from the Alps across the Jura, the great plains 

 of the Doubs and the Soane, the southern prolongation 

 of the Vosges, and, over the separating water-shed formed 

 by the lower hills of Burgundy, to the Seine basin, and so 

 to sea on the northern shores of France. Such a cata- 

 clysm must surely have spread the debris of the strata 

 destroyed in its course north-westward along the tract 

 over which it flowed. Some remains of the rocks of 

 Switzerland, of those of the Vosges and of Burgundy, 

 must surely have been detected in the course of 

 its passage. How can the author account for the 

 large blocks and abundant debris of the Seine valley 

 — which blocks and debris he considers as originally 

 due to this cataclysmic action — and yet overlook the 

 almost necessary consequence of the introduction of 

 some foreign elements into the Seine Basin, whereas none 

 such exist. Not only is the debris of each gre.it Lasin 

 restricted to its own rocks, but even each tributary river 

 valley has its own special rock debris and no other. M. 

 Belgrand remarks, it is true, of the Somme Valley, which 

 lies on the line of his third great diluvial water channel, 

 and which prolonged south-east passes across the Oise 

 valley and up that of the Aisne, that some dSris of the 

 older rocks of the latter areas have been found in the chalk 

 valley of the Somme. But we must confess we have never 

 found a trace of such a mixture, and we have particularly 

 examined the Drift of those areas with a view to the de- 

 termination of this point. At the same time the water- 

 shed between the two valleys is so low that their complete 

 separation in old times appears to us more remarkable 

 than their present independence, and we can quite con- 

 ceive the possibility of the Oise waters, when that river 

 flowed at its higher level, passing at periods of flood into 

 the valley of the Somme, and so carrying some small 

 amount of debris across the present water-shed, espe- 

 cially as so good an observer as M. Buteux is referred to 

 as the authority for this fact. If there, however, it is 

 evidently quite the exception, and may be accounted for 

 as just suggested. 



With regard to the ingenious suggestion of M. Belgrand 

 that some south-east and north-west valleys of the table- 

 lands are faced on the opposite side of intersecting river 

 valleys by a bay in the hills due to the violence of the 

 checked diluvial waters, such for example as the amphi- 

 theatre in the hills on the west of the River Ecolle 

 between Milly and Moigny and again at Soissy, it is to 

 be remarked that such amphitheatres exist equally on the 

 opposite or lee side of the hills towards La Fertd-Aleps 

 and Maisse ; and, further, that, in the same Tertiary area 

 beyond the intersecting range of hills between the Ecolle 

 and the Essonne (which according to M. Belgrand's views 



