It is unnecessary for me to remind the readers of the Geological Magazine of the evidence for elevation and subsidence. For my present purpose it is sufficient to remind them that suoh elevation and subsidence has been attributed (1) to lateral pressure giving rise to long geo-anticlines and geo-synclines; (2) to expansion and contraction of the underlayers resulting from a rise or a fall of temperature; and (3) to the loading and unloading of the areas of the earth's crust affected. Apparent elevation and subsidence, which we may here neglect, may be due to a rise or fall of the sea-level such as is dealt with by Prof. Hull in a recent communication to this Magazine.