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Hence we may admit that periods of slow subsidence will commonly be most favourable to the accumulation of CONCHIFEROUS deposits, of sufficient thickness, extension, and hardness, to resist the average powers of denudation.
Nor will I again give the facts and reasoning on which the proposition was founded, that when the bed of the sea is either stationary or rising, circumstances are far less favourable than when its level is sinking, to the accumulation of conchiferous deposits of sufficient thickness, extension, and hardness to resist, when upheaved, the ordinary vast amount of denudation.
Amidst the first strata I suffered the watery action to expend itself upon cooling, crystallized masses; and by the time I had got him into the tertiary period, amongst the transition chalks of Maestricht and the conchiferous marls of Gosau, he was ready for a new wife. Kitty, my dear, it is no laughing matter!
Amidst the first strata I suffered the watery action to expend itself upon cooling, crystallized masses; and by the time I had got him into the tertiary period, amongst the transition chalks of Maestricht and the conchiferous marls of Gosau, he was ready for a new wife. Kitty, my dear, it is no laughing matter!
Smooth, dark gray tophus predominates; it forms the bed of the Rio Pasig, and rising forms hillocks in the vicinity of the city of Binangonan. Farther on, trachyte and banks of conchiferous sand predominate. The vast plain of Panpanga extends to the north of Manila Bay, to the south of which is situated Mount Arayat, of doleritic nature.
A whole conchological series will in time be swept away, with no memorials of their existence preserved in the earth's crust. Can any light be thrown on this remarkable absence of recent conchiferous deposits on these coasts, on which, at an ancient tertiary epoch, strata abounding with organic remains were extensively accumulated?
First, let us take the case of the bed of the sea long remaining at a stationary level: under these circumstances it is evident that CONCHIFEROUS strata can accumulate only to the same thickness with the depth at which the shells can live; on gently inclined coasts alone can they accumulate to any considerable width; and from the want of superincumbent pressure, it is probable that the sedimentary matter will seldom be much consolidated: such formations have no very good chance, when in the course of time they are upraised, of long resisting the powers of denudation.
From the foregoing reasoning, and from the facts just given, I think we must admit the probability of the following proposition: namely, that when the bed of the sea is either stationary or rising, circumstances are far less favourable, than when the level is sinking, to the accumulation of CONCHIFEROUS deposits of sufficient thickness and extension to resist, when upheaved, the average vast amount of denudation.
Considering these facts, it ceases, I think, to be surprising, that extensive recent conchiferous deposits are entirely absent on the southern and western shores of America. Let us take the one remaining case, of the bed of the sea slowly subsiding during a length of time, whilst sediment has gone on being deposited.
Excavations on the hill of Hissarlik, begun by Dr. Schliemann in 1871, and carried on under his superintendence for more than ten years, have, on the contrary, yielded most definite, satisfactory, and conclusive results. At a depth of fifty-two feet the diggers came to the virgin soil, a very hard conchiferous limestone.
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