328 A.C. Ramsay on the Glacial origin of certain Lakes 
oa the prodigious glacier of the Rhone that abutted on the 
ura 
Connection between Tarns and Glaciers.—In The Old Glaciers of 
in diameter. Sometimes in the convolutions of the strata (con- 
joined with preglacial denudation subsequent to the contortion 
of the beds), softer parts of the country may have been scooped 
out, leaving a hollow surrounded by a frame-work of harder 
rock; but perhaps more generally they were formed by the 
greater thickness and weight, and consequently proportionally 
greater grinding pressure, of glacier-ice on particular areas, due 
to accidents to which it is now often difficult-or impossible to 
find the clue. rifling as this phenomenon at first sight may 
seem, I yet believe the manner of the formation of these lake 
is of much importance to the right understanding of the glacial 
theory, whether taken in connection with the great extension of 
extinct glaciers in recognized glacier-regions, or, further, when 
viewed on a general continental scale; for the theory @ 
cial origin of many rock-basins must, I feel convinced, be && 
tended much beyond such mountain-districts as Switzerlan¢ 
Wales, and the Highlands of Scotland, where they first a 2 
my attention.° the 
gin of the Great Alpine Lakes, subject stated—Vrom ae 
consideration of the origin of mountain-lakes and tarns, 
question easily arises,—What are the causes that_have operai” 
in the formation of the great lakes of Switzerland, such as ‘at 
of Geneva, Zurich, and Constance, and, south of the oa 
Maggiore, Lugano, Como, and others? To answer this 
a it will be necessary, first, to examine 
ypotheses that by some may be thought sufficient to 
for them. : 
It is well known that after the close of the Miocene ep? - 
the rocks of the Alps were much disturbed,—a ciroumstam 
* Quart. Journ, Geol. Soc. Lond. 1851, viii, 871; and The Old Glaciers of ee 
® Tt is not to be supposed that I attribute the origin of all rock-basins t0 8 or 
action, Many lie a te craters of extinct volcanos, some, no doubt, 10 ste 1 
special subsi , and others may be due to causes of which I ; 
now | my remarks to certain lakes common in all highly 
