still very ignorant of many details of ice action, and
especially of the origin of many enormous deposits which are not true
moraines." Such deposits are referred to as occurring in the Yangma
valley.) Your not having found scored boulders and solid rocks is an
objection both to glaciers and floating ice; for it is certain that
both produce such. I believe no rocks escape scoring, polishing and
mammillation in the Alps, though some lose it easily when exposed. Are
you familiar with appearance of ice-action? If I understand rightly, you
object to the great dam having been produced by a glacier, owing to the
dryness of the lateral valley and general infrequency of glaciers in
Himalaya; but pray observe that we may fairly (from what we see in
Europe) assume that the climate was formerly colder in India, and when
the land stood at a lower height more snow might have fallen. Oddly
enough, I am now inclined to believe that I saw a gigantic moraine
crossing a valley, and formerly causing a lake above it in one of the
great valleys (Valle del Yeso) of the Cordillera: it is a mountain of
detritus, which has puzzled me. If you have any further opportunities,
do look for scores on steep faces of rock; and here and there remove
turf or matted parts to have a look. Again I beg, do not give up
Geology:--I wish you had Agassiz's work and plates on Glaciers. (501/4.
"Etudes sur les Glaciers." L. Agassiz, Neuchatel, 1840.) I am extremely
sorry that the Rajah, ill luck to him, has prevented your crossing
to Thibet; but you seem to have seen most interesting country: one is
astonished to hear of Fuegian climate in India. I heard from the Sabines
that you were thinking of giving up Borneo; I hope that this report may
prove true.

LETTER 502. TO C. LYELL. Down, May 8th [1855].

The notion you refer to was published in the "Geological Journal"
(502/1. "on the Transportal of Erratic Boulders from a lower to a higher
Level." By C. Darwin.), Volume IV. (1848), page 315, with reference to
all the cases which I could collect of boulders apparently higher than
the parent rock.

The argument of probable proportion of rock dropped by sea ice compared
to land glaciers is new to me. I have often thought of the idea of the
viscosity and enormous momentum of great icebergs, and still think that
the notion I pointed out in appendix to Ramsay's paper is probable, and
can hardly help being applicable in some cases. (502/2. The paper by
Ramsay has no a