Dear Sir

I have been prevented by long continued illness from not having many months since sent you my sincere thanks for your most valuable pamphlets on meter-eology¹ (which, however, I do not feel worthy to receive from the little attention I have paid to that great branch of science), and the Geological Reports² some of which I have been able to peruse & have been much interested by them.

As I am yet far from recovered I beg you will excuse the lateness & briefness of this letter & believe me dear Sir | Yours very faithfully | Charles Darwin

Postscript | With respect to the late discussions on the rotatory action of whirlwinds, I will just mention a trifling observation I noticed in Bruce’s travels,³ where he describes the sublime appearances, presented by the great whirling columns of sand, on his return home across the Nubian desert.— He especially says that the whirling movement had left traces or concentric furrows (?) on the pointed conical hillocks of sand, with which the plain in parts were scattered.— These hillocks having been left, when the columnar mass of sand broke.— I quote only from memory.—

P.S. 2^d. As I have mislaid your letter, I am compelled to direct this to the care of Prof. Silliman, who, I daresay, will excuse the liberty.—