OF THE EARN AND TEITH. 173 



those of France and England, the long period required for the supposed lower- 

 ing of the river-bed is got rid of. If the stream which flows through the valley 

 at Brixham could do what has been done by the burn in the valley of Monzie ; 

 or if the Somme could do what the Teith has done along its course, any amount 

 of high-level gravels might have been piled up, or carried into caves after the 

 valleys had been hollowed out, and the bed of the stream brought down to 

 where it now is. 



But are we right in supposing that the analogy of our Scottish rivers will 

 apply to those of England and France ? The presumption certainly is that 

 their formation was analogous.""" But we have more than mere presumption. 

 Mr Tyler, an English geologist, has been investigating the case of the Somme, 

 and finds evidence of a pluvial period — a time of high floods sufficient to 

 account for the high-level gravels. The body of facts which he has brought 

 together deserve careful consideration, and it will certainly be matter of deep 

 interest if the deposits of the Somme are found to record the same story whicli 

 we have been reading along the Earn and Teith.t 



I have no wish to push this argument beyond what is perfectly fair. These 

 terrace-like deposits form a subject which has been too little investigated. It 

 may turn out that they reveal to us a period of river floods much greater in 

 volume than men are generally prepared as yet to admit. And it may also be 

 that those inferences which have been drawn as to the duration of the human 

 period may be very seriously affected. It would surely be safe to have more 

 complete examination before judgment is given. These deposits belong to what 

 in geology is a very recent period indeed, and all I would ask is that the facts 

 be more fully investigated, lest in arguing for extreme views as to the antiquity 

 of the race men be found importing fallacious elements into the calculation. 



But how shall we account for the volume of water necessary to produce 

 such floods f Looking to the width of some of our valleys, and to the height 

 of these deposits, is it not difficult to believe in the existence of such torrents \ 

 In dealing with this question care must be taken not to exaggerate the diffi- 



* An attempt has been made to deny this on the ground that Scotland was submerged during the 

 glacial epoch, while Picardy and Devonshire were not — the object being to show that the French 

 valleys were excavated at a later period than the Scottish. But this argument can hardly be urged by 

 those who hold that the formation of valleys is due mainly to subaerial forces and hardly at all to 

 marine action. If the difference between the two countries be that Erance not having been submerged 

 was continuously acted on by these eroding agencies, while Scotland was withdrawn from them by 

 being buried beneath the sea, how will that prove the French valleys to be of later formation than the 

 Scottish 1 So far as that difference goes it should surely prove the reverse. 



t " On the Amiens Gravel," by Alford Tyler, Esq., F.G.S., " Journal Geol. Soc. Lond." vol. xxiv. 

 p. 103. In one respect Mr Tyler's reading is different. He regards the lower terrace, the loess, as 

 the bank of the ancient river when in its ordinary state, and the higher terrace as its bank when in 

 flood — referring both to the same period. This differs materially from the view which I have been led 

 to take, namely, that each terrace is the highest flood-mark of its own time, just as the present banks 

 aud haughs are related to the floods of the present time. 



VOL. XXVI. PART I. 2 Z 



