^{page 109 note 1} Although subœrial or atmospheric denudation are the received names for the first class of denudation, yet neither seems unobjectionable; for, strictly speaking, all denudation is subcerial and all is caused by atmospheric influences, as all mechanical denudation, without these influences, would be nil. Difference of temperature causes the wind, the oceanic currents, and the glaciers, also the evaporation that eventually forms the rain and rivers. When it is said “Ice is one of the subserial agents,” the statement is quite correct; hut if “Subærialists” claim its action, they ought also to claim marine denudation; for, without the atmospheric influences, there would be no oceanic currents, no tidal currents, no storms—in fact, no denuding action at all. On the other hand, “Marinists” might claim all work done by rain and rivers, as they were originally sea water, which, previous to leaving, had taken “a return ticket” to go by the atmospheric way and come back by the river.

In the first of the above divisions (Subærial or Atmospheric denudation) is included all the work done by the chemical action of the atmosphere and the mechanical work by rain and rivers. This seems to have been the original doctrine of the “Subterialists,” although of late they would wish to include all glacial work. Seemingly a less objectionable name than either Subserial or Atmospheric would be chemical denudation, but, perhaps, a better still would be Chemico-fluvial denudation, as this latter term would include not only the chemical action due to Atmospheric influences, but also the mechanical work doue by rain and rivers.

^{page 110 note 1} Hayes says “The ice was perfectly pure and transparent” (of “Tyndall glacier”), “and yet out of its very heart was pouring the muddy stream of which have made mention.”—“The Open Polar Sea.” p. 436.

^{page 111 note 1} See short notes on this subject by the writer, Geol. Mag. Vol. V. p. 18Google Scholar.

^{page 111 note 2} Capt. Forbes, R.N., in “Iceland, Its Volcanos, etc.,” pp. 281, et sequit. mentions huge debacles caused by glaciers being loosened and displaced by volcanic heat.

^{page 114 note 1} The disappearance of stones, etc., needs no growth of soil. It has been explained by Darwin “On formation of mould,” Trans. Geol. Soc.—[ED. Geol. Mag.]