My dear Sir

By some accident I received your note only this morning, for which I am much obliged; as it w^d. be very inconvenient to me to attend I would much rather not be on the Committee. Indeed it w^d. be superfluous, as I know not much of the Nat. History of N. America, & as Sir Roderick Murchison & D^r. Hooker are on it.³ Sir John Richardson would be the man for Zoological suggestions.—

As the extension in Lat. & Long. & all the phenomena of Glacial action & erratic boulders will, no doubt, be one chief object of attention to the geologist of the Expedition, I may make one suggestion, viz to attend most carefully to the state of the rocks in those rivers, in which annually large quantities of ice are carried down with great force. Sir John Richardson many years ago, told me that they were beautifully polished.—⁴ Are they scored also? & is the scoring on the upper side. &c &c.— are stones & mud embedded in river ice? It is a great desideratum in geology to be able to distinguish between rocks polished & scored by glaciers, & by floating ice.—⁵

I suppose the expedition will not visit any arctic shore; but it may fall across some ancient line of cliff, with beds of shingle at its base, formed during the Glacial epoch, & I think a most minute examination of the character of the shingle on arctic shores would be very desirable, for comparison with the sub-angular drift of the southern counties of England. The tertiary strata with fossil plants & lignite would be a very interesting point for examination; but is quite obvious.— If I sh^d. think of any point worth noticing, I will write.

Pray believe me, my dear Sir | Yours sincerely | Ch. Darwin