WCP2259

[1]

Geological Survey Office

Edinburgh

Sept 28/70

Dear Sir

Thanks for your favour which came to hand this morning¹.

My calculations were simply made from Leverrier² formula but I cannot but I cannot pretend to be able to discuss the merits of the formula [illeg.] ^themselves. But the very idea that a formula for determining the Secular changes in of [2] the earth's orbit can only be depended upon for a few 10,000 years is so absurd as not be worth [sic] of consideration.

M^r Stone³ of Greenwich Observatory, one of the highest authorities we have, in a letter to Sir Charles Lyell stated that he had given this formula special consideration and found that they may be relied upon as giving pretty correct results for a period of at least 4,000,000 years back.

[3] Of course the Russian mathematician is right as regards the precession of the equinoxes. But this is of no importance. We know that there has always been precession and this is enough.

In my former paper on the Motion of Glaciers, a copy of which I think I sent to you, I have attempted to show that crevasses follow ^as a necessary consequence from the Molecular theory.

If I understand your views correctly ^{a glacier} could not

x Phil-Mag March 1869⁴

[4] have any motion if its width slope and direction were uniform, for the pressures at the various points would then remain constant; and the peculiar conditions which you suppose could not exist.

But would not such a glacier descend?

Of course I gave out the idea as simply a hypothetical explanation of the mystery and it must just be taken for what it is worth. I shall be glad to see a report of your interesting paper and discussion.

Yours [illeg.] | James Croll⁵