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Should it, however, be ascertained that the larger amount of loose material spreading over the harbor is derived from some one or other of the drift islands in the bay, the building of sea-walls to stop the denudation may be of greater and more immediate use than any other operation.
RATE OF DEPOSITION. As deposition in the sea corresponds to denudation on the land, we are able to make a general estimate of the rate at which the former process is going on.
It is impossible to behold such effects of reiterated local movements, all of post-Tertiary date, without reflecting that, but for the accidental presence of the stratified drift, all of which might easily have been missing, where there has been so much denudation, even if it had once existed, we might have referred the verticality and flexures and faults of the rocks to an ancient period, such as the era between the Chalk with flints and the Maestricht Chalk, or to the time of the latter formation, or to the Eocene, or Miocene, or Pliocene eras, even the last of them long prior to the commencement of the glacial epoch.
I should observe that in the autumn, soon after the vintage, the earth is heaped up round the vines to protect them from the intense cold which prevails here, and directly the spring comes, one must open up the vines again. In Tokay the vines are never trellised, they are disposed irregularly, not even in rows the better to escape the denudation of their roots by rain.
The soil, formed of the denudation of the sandstone rocks, scantily fertilised here and there by the decaying jungle, presented no field for rude agriculture, even had the dry seasons permitted; and gave forth no native fruits, save tasteless berries and half-poisonous roots.
Before we consider how the waste of the land brought in by streams is rebuilt upon the ocean floor, we must proceed to study the work of two agents, glacier ice and the wind, which cooperate with rivers in the denudation of the land.
Assuming this rate of denudation as certain, and also the estimate of the known sedimentary strata as 177,000 feet in depth, we are to conclude that the formation took 56,000,000 years. A mountain mass which ought to answer to certain fault 15,000 high, and therefore is presumed to have vanished by denudation, points to a term of 90,000,000 years as required for the process.
If these most ancient beds had been wholly worn away by denudation, or obliterated by metamorphic action, we ought to find only small remnants of the formations next succeeding them in age, and these ought to be very generally in a metamorphosed condition.
Looking over the hills, it struck the fancy at once that at one period the whole land must have been at a uniform level with their present tops, but that by the constant denudation it was subjected to by frequent rains, it had been cut down and sloped into those beautiful hills and dales which now so much pleased the eye; for there were none of those quartz dykes I had seen protruding through the same kink of aqueous formations in Usui and Karague; nor were there any other sorts of volcanic disturbance to distort the calm quiet aspect of the scene.
Evidence of the amount of denudation which the land has undergone Sub-aerial denudation The deposition of dust Vegetable mould, its dark colour and fine texture largely due to the action of worms The disintegration of rocks by the humus-acids Similar acids apparently generated within the bodies of worms The action of these acids facilitated by the continued movement of the particles of earth A thick bed of mould checks the disintegration of the underlying soil and rocks.
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