Comments on DM’s ["The Moel-Tryfan shelly deposits", Q. J. Geol. Soc. Lond. 37 (1881): 351–69].

Comments on cause of earthquakes.

Believes formation of ice lowered level of sea.

Has found three zones of stones in the Welsh and Pennine mountains which he accounts for by elevation and subsidence. Does CD think that these movements in historical times have been caused by earthquakes or by slow and gradual movements?

The use of earthquakes as a geological cause in his previous letter was careless.

Shelly beach deposits over considerable distance from Ireland to Scotland seem better explained by high sea-level than low land.

Only CD seems to have reported shattered rocks under the Moel Tryfan drift.