1882 .] 
327 
[Davis. 
the latter, a small part of the great meadow is unfilled, and holds 
Lake Walar 1 (see C. 12). 
In the Jura Mountains a number of small lakes occupy troughs 
formed by down-folded strata, but I cannot learn whether they 
may not be held back by local deposit barriers. The Lac de Joux 
is marked at its northeast end by a strong cross-fault. 2 The other 
basins hold Lacs de St. Point and des Rousses, as well as the extinct 
lakes of the Val de Pontarlier and the Val de Travers. A little 
farther south the Lac de Bourget is a good example of its kind. 
Guyot considers Lake Neuchatel the result of local depression. 8 
The absence of lakes in the Appalachians south of New York 
was noticed as a peculiarity by Lyell 4 ; if any* ever existed, they 
have long been destroyed by erosion, and when the Jura are as old 
as the Appalachians they will probably be as lakeless. Indeed, the 
rarity of small lakes distinctly referable to this species points 
to the complete and searching work of the erosive forces that 
are constantly at work cutting down valley barriers, rather than 
to the original absence of basins of downfolding. It is hardly 
possible that in a region so disordered as the Alps no trough- 
basins should have been formed during the extreme crushing to 
which the strata there have been subjected; we should better 
suppose that such basins were made, but were cut down at one 
side nearly as fast as they were folded into shape, and so were 
transformed into lakeless valleys. The valleys of the Rhone above 
Martigny, and of the Rhine above Chur, mark the sites of such 
attempted lakes ; perhaps lakes may have existed there for a time, 
but as the transverse exit-valleys were cut down, the basins were 
opened and drained. 5 The marginal lakes of the Alps are noticed 
farther on. 
A. 3. Fault Basins. These are very rare, and point to 
the slow growth of dislocations as well as to the careful work of 
water erosion, as does the preceding species. Lough Allen, near 
1 Medlicott and Blanford, Geol. India, ii, 672. Drew, Jummoo and Kashmir, 207. 
2 See sheet of xi the Swiss Geol. Commission. 
3 Neuchatel M^m., in, 1845. 
4 Travels in the United States, 1845, ii, 240. 
6 Riitimeyer, Thai und Seebildung, 95. Jukes, Geol. Soc. Journ., xvm. 1862, 378 . 
