Edward Merrick — The River Tyne Drainage Area. 353 



lakes banked by fluviatile bars are clearly post-Glacial. On the other 

 hand, Lake Klontal and Lac de Joux lie in old pre-Glacial valleys, 

 of which that of the former was no doubt filled with or choked by 

 the Glarnisch Glacier, upon whose retreat the lake was formed. 

 Lakes Neuchatel and Lienne occupy the trough of the contact line of 

 the Jura and the Molasse formations, and, lying in the zone of the 

 Rhone Glacier, 1 were probably formed during the retreat of the 

 latter; but both, as well as Lake Morat, were subsequently banked 

 by the post- Glacial alluvia of the A are. 



2. The remarkable shrinkage of all the smaller lakes, compared 

 with the much larger areas covered by them at the time of their 

 formation, cannot be due to want of precipitation, for neither north 

 nor south of the Alps is there any marked diminution of the annual 

 rainfall. The cause must therefore be sought in gradually increasing 

 loss of water by evaporation and percolation. Increased solar heat 

 during dry summers causes increased melting of the glaciers and 

 superabundance of water in the lakes and lowlands, which is, 

 however, generally followed by a shortage of supply in winter, so 

 that the increased evaporation of the lakes in summer is not com- 

 pensated by additional volume of water in winter. 2 Still greater is 

 the loss by percolation through the dry soil of the drainage areas and 

 the permeable rock strata below, by which, as shown by the dried-up 

 basins of the Jura and certain quasi-dried up valleys in the lowlands, 

 large masses of water are abstracted from the surface and circulate 

 underground. The gradual shrinkage not only of the smaller lakes 

 but of the five principal zonal lake basins as the great hydraulic 

 storage and regulation reservoirs of Switzerland would be a disquieting 

 phenomenon were it not that the areas dried up are so much land 

 reclaimed, and that the shrinkage itself may be but a cycle in the 

 •evolution and lapse of time. 



V. — On the Formation of the River Tyne Drainage Area. 



By Edward Merrick, M.Sc. 



(Concluded from the July Number, p. 304.) 



D. The Earth-Movements considered Stratigraphicallt. 



AN important factor in the formation of this drainage area as above 

 outlined is the movement of the rocks after they had been 

 reduced to a surface comparable with a peneplain. These movements 

 are now reviewed to see if any assumptions have been made which 

 are probably incorrect from stratigraphical evidence. 



1. The Stublick Dyke was supposed to be later than the formation 

 of the junction plane, else it could not affect the contours as indicated 

 on the north of itself and the Tyne. 



1 The boulders of Shone Valley (Valaiz) origin on Mt. Chaumont above 

 Neuchatel, at an altitude of 1,220 metres or 785 metres above the lake, were 

 deposited by the Rhine Glacier of the maximum glaciation. 



2 Of this frequent shortage in winter, practical proof is afforded by the fact 

 that most, if not all the large Swiss bydro-electric power installations have 

 added reserve steam-power to their hydro-turbines to meet that shortage. 



DECADE VI. — VOL. II. — NO. VIII. 23 



