To F. B. Zincke   3 November 1881

Dear Sir

I am much obliged for your letter. The case of the celts on the pan is very curious, on account of the depth of 3 ft & more especially because the lower 18 inches is described by you as “sandy loam” & therefore as differing from the upper 18 inches of black mould. If the celts had been buried wholly by worms, I sh^d. have expected that the whole 3 ft would have consisted of black mould.¹ This case leads to the enquiry whether the carbonaceous matter does not disappear at a depth at which no more vegetable matter is regularly added. The enquiry is new to me; but it seems possible as carbonaceous matter in the soil, if not too wet, can oxidise & disappear.—

With respect to the large arctic mammals, anyone might maintain that large size was an advantage in retaining warmth, from the relatively small superficies, compared with smaller mammals.

The number of whales, walrusses narwhals in the artic seas & of huge seals in the antarctic seas, may possibly be thus explained.—

Again thanking you for your letter, I remain | Dear Sir | Yours faithfully | Ch. Darwin