326 Prof. Strider on Bowlders. 
the interior of Switzerland, had only a very small depth and al- 
ternated with dry land such as we now regard as low land, (tief 
land); and, finally, that the elevation of the Alpine chain could 
scarcely have been an instantaneous thrusting up of the whole 
mountain mass, in which the sea might have been slung on 
high with it, but a very complicated process continued through a 
long space of time.* The great depth of the Swiss lakes has 
ever been the principal objection with the opponents of that ex- 
planation, and the ease with which the new ice and glacier theory 
sets aside this difficulty, accounts of itself for the interest with 
which it has been received. The difficulty lies not, as I think, 
in carrying the detritous streams and blocks over the lakes. 
The water-course could do no more than force a part of the wa- 
ter of the lake, and, considering the small difference of specific 
gravity, the height and rapidity of the streams, hardly a very 
important part, out of its basin and mingle with it; had the 
stream at once poured itself out entirely over the whole lake, in 
that case the back portion of the detritus would flow on over it, 
as we see the upper water in our lake move over the deep, still 
water. The separation of the solid materials from the detritous 
water might to be sure raise the bottom of the lake, yet not 
more than we see the bottom of the molasse-vallies now elevated 
in many places by diluvial ruins, that is, at the highest one hun- 
dred feet. Nor is it difficult of solution why the basins of the 
lakes have not been entirely filled up by the later transportation 
of smaller blocks such as have occurred in part within the his- 
torical period ; for, originally these blocks were not, as is gene 
rally supposed, so naked and free, as we now see them, but cov- 
ered with thick coatings of rubbish. This appears very clearly; 
among other examples, in the immediate neighborhood of Berne. 
A row of low hills stretches in an arch convex to the west across 
the Aar-valley close to the west end of our city, which has 
its contiguous eminences for breast-works. In the late demoli- 
tion of the fortifications, these eminences which were universally 
supposed to be works of art thrown up on the common level of 
the ground, were penetrated to their center and it was found that 
they consisted for the most part of enormous heaps of Alpine 
GR eRe’, cites 
* The imbedding among the diluvial ruins of the blocks at Stratligen and Utz 
nach, of unchanged pines and firs, plants and insects of the present time in brown 
coal, appears to place the spread of this detritus at a very recent epoch. 
