156 Geological Notes on the 



ancient barriers. In reality, the discharge of lakes by the 

 giving way of their barriers is a rare event in nature ; and 

 when it does take place, there can scarcely fail to be some 

 remains of the barrier to commemorate the event. It has 

 not been observed, that the phenomena in question are pre- 

 sented more or less conspicuously in every valley, while in- 

 dubitable appearances of ancient barriers are scarcely any 

 where pointed to, and in many cases it is inconceivable how 

 they could have either been formed or removed. For in- 

 stance, in the present case, no barrier in the valley of the 

 Rhone would suffice to sustain the waters of Lake Leman at 

 442 feet above their present level, seeing that, on their ex- 

 ceeding a rise of 240 feet, they would pass over the height 

 of the country between Geneva and Neufchatel, and conse- 

 quently be discharged into the valley of the Rhine. The idea 

 of lake barriers, indeed, appears to be the mythical stage of 

 the investigation. When many valleys have been carefully 

 examined, without presenting a single feature in support of 

 this action, it becomes an unavoidable alternative, that we 

 suppose the sea to have formerly stood at a higher level — I 

 do not say, absolutely, but in relation to the land, so as to fill 

 the valleys with estuaries, and be concerned in the formation 

 of these ancient alluvia. I venture to affirm, that no one 

 could examine many valleys as I have done, and invariably 

 trace such alluvial formations from the open country near 

 the sea, without any interruption up to the base of the great 

 chains of hills from which the rivers originated, without con- 

 cluding that the only recipient body of water concerned in 

 the case was the sea. 



Under this view, it becomes of importance to learn how 

 high such formations can be traced in the Alpine valleys. 

 We have already adverted to examples at Basle, between 

 900 and 1000 feet above the level of the sea, and to the an- 

 cient alluvia of the Arve valley, which ascend to nearly twice 

 this elevation. But these do not express the full height 

 which the sea has attained in these vales during the alluvial 

 period. The Lake of Thun is 1875 feet above the sea. Its 

 affluent, the Kander, passes through gravel terraces, which, 

 at no great distance from the lake, are at least 150 feet above 



