WCP6888

[1]

Parkstone, Dorset.

July 7th, 1893.

Dear Mr Fisher

I have been away a week in Derbyshire among the beautiful limestone dales, or should have sent you a few lines earlier. I see now my error about the balance adding to the effect of weight. But there are so many complexities to this problem that I get continually perplexed.

I see in an article on "The New Geology" in "Knowledge," November 1 1892 it is stated that Prof. Suess maintains that continental elevations, as opposed to mountain elevations, are due [2] to variations of sea-level, but how caused is not explained. Have you ever gone with the problem of attraction of mountain masses altering sea level ? Some have said that it is great enough to account for all the apparent elevations and depressions of lowlands. For instance, if the Andes were removed to the East side of S. America, would there still be a change of ^relative level of the Atlantic & Pacific to the extent of some hundreds of feet; and I presume the [3] change of level with be the same whether the transformations were affected in one year or in 10 million years. I sh^d think that, as a dynamical problem it would be easier than your crust- & sub-stratum problems.

I am going next week to the Lakes, for a month or so. I have never seen them, and I have to get a little light on the the glacier-lake theory which I am immensely interested in. At present the arguments in favour seem to be much stronger than those against it.

[4] The Alpine men — Bonney, Freshfield, Whymper &c. are all against it but they think it can be settled by simple & direct observation of existing glaciers, whereas it requires much careful reasoning on facts chiefly dependent on size & agency of extinct glaciers and ice-sheets. I have been trying to hit upon some crucial facts, and I think I have found them,— that is facts which on one theory ought to exist & not in the other. But these facts depend on the exact contours of lake bottoms & the valleys in which they exist, & this is difficult to get at.

Yours very truly | Alfred R. Wallace [signature]