unload my mind on paper.
I thought everything so beautifully clear about glaciers, but now your
case and Agassiz's statement about the cavities in the rock formed by
cascades in the glaciers, shows me I don't understand their structure at
all. I wish out of pure curiosity I could make it out. (499/1. "Etudes
sur les Glaciers," by Louis Agassiz, 1840, contains a description of
cascades (page 343), and "des cavites interieures" (page 348).)

If the glacier travelled on (and it certainly does travel on), and the
water kept cutting back over the edge of the ice, there would be a great
slit in front of the cascade; if the water did not cut back, the whole
hollow and cascade, as you say, must travel on; and do you suppose the
next season it falls down some crevice higher up? In any case, how in
the name of Heaven can it make a hollow in solid rock, which surely must
be a work of many years? I must point out another fact which Agassiz
does not, as it appears to me, leave very clear. He says all the blocks
on the surface of the glaciers are angular, and those in the moraines
rounded, yet he says the medial moraines whence the surface rocks come
and are a part [of], are only two lateral moraines united. Can he
refer to terminal moraines alone when he says fragments in moraines are
rounded? What a capital book Agassiz's is. In [reading] all the early
part I gave up entirely the Jura blocks, and was heartily ashamed of my
appendix (499/2. "M. Agassiz has lately written on the subject of the
glaciers and boulders of the Alps. He clearly proves, as it appears to
me, that the presence of the boulders on the Jura cannot be explained
by any debacle, or by the power of ancient glaciers driving before them
moraines...M. Agassiz also denies that they were transported by floating
ice." ("Voyages of the 'Adventure' and 'Beagle,'" Volume III., 1839:
"Journal and Remarks: Addenda," page 617.)) (and am so still of the
manner in which I presumptuously speak of Agassiz), but it seems by his
own confession that ordinary glaciers could not have transported the
blocks there, and if an hypothesis is to be introduced the sea is much
simpler; floating ice seems to me to account for everything as well
as, and sometimes better than the solid glaciers. The hollows, however,
formed by the ice-cascades appear to me the strongest hostile fact,
though certainly, as you said, one sees hollow round cavities on present
rock-beaches.

I am glad to observe that