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The faces of the joints are for the most part smoother and more regular than the surfaces of true strata. The joints are straight-cut chinks, sometimes slightly open, and often passing, not only through layers of successive deposition, but also through balls of limestone or other matter which have been formed by concretionary action since the original accumulation of the strata.
Hence, after this limestone with its shells was deposited, the bottom of the sea where the main line of the Cordillera now stands, must have subsided some thousand feet to allow of the deposition of the superincumbent submarine strata.
The intensity of these underground forces continues to diminish. Volcanoes were quite numerous in the world's early days, but they're going extinct one by one; the heat inside the earth is growing weaker, the temperature in the globe's lower strata is cooling appreciably every century, and to our globe's detriment, because its heat is its life." "But the sun " "The sun isn't enough, Conseil.
The succession of strata here alluded to would be consistent with the occurrence of gradual downward and upward movements of the land and bed of the sea without any disturbance of the horizontality of the several formations. But the arrangement of rocks composing the earth's crust differs materially from that which would result from a mere series of vertical movements.
With a name suggestive of the purest English origin, Mr. Hardy has become identified with that portion of England where the various race-deposits in our national "strata" are most dear and defined.
In mineral character this group forms a transition from the Silurian to the Old Red Sandstone, the strata of both being conformable; but it is now ascertained that the fossils agree in great part specifically, and in general character entirely, with those of the underlying Upper Ludlow rocks.
The seams of coal were separated by strata of sandstone, a compact clay, which appeared to be crushed down by the weight from above. At that period of the world which preceded the secondary epoch, the earth was covered by a coating of enormous and rich vegetation, due to the double action of tropical heat and perpetual humidity.
It will, therefore, be proper to consider, what are the appearances in consolidated strata that naturally should follow, on the one hand, from fluidity having been, in this manner, introduced by means of heat, and, on the other, from the interstices being filled by means of solution; that so we may compare appearances with the one and other of those two suppositions, in order to know that with which they may be only found consistent.
In the common salt by which strata are often largely impregnated, as in Patagonia, much soda is present, and potash enters largely into the composition of fossil sea-weeds, and recent analysis has also shown that the carboniferous strata in England, the Upper and Lower Silurian in East Canada, and the oldest clay-slates in Norway, all contain as much alkali as is generally present in metamorphic rocks.
There seems, then, no escape from the admission that neither physical geology, nor paleontology, possesses any method by which the absolute synchronism of two strata can be demonstrated. All that geology can prove is local order of succession.
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