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Even before they have attained a great depth, through the laying down of later deposits upon them, changes begin which serve to alter their structure. The fragments of a soluble kind begin to be dissolved, and are redeposited, so that the mass commonly becomes much more solid, passing from the state of detritus to that of more or less solid rock.
In such cases we are reminded that, the same materials having been used over and over again, it is not enough to affirm that the entire mass of stratified deposits in the earth's crust affords a monument and measure of the denudation which has taken place, for in truth the quantity of matter now extant in the form of stratified rock represents but a fraction of the material removed by water and redeposited in past ages.
M. d'Orbigny has suggested that all these mammiferous remains may have been washed out of the Pampean formation, and afterwards redeposited together with the recent shells. In the first place, it should not be overlooked, that most of the co-embedded shells have a more ancient and altered appearance than the bones.
The presence of any fresh-water infusoria, considering the aridity of the surrounding country, is here remarkable: the most probable explanation appears to be, that these microscopical organisms were washed out of the adjoining great Pampean formation during its denudation, and afterwards redeposited. We will now see what conclusions may be drawn from the facts above detailed.
The salinas occur at different elevations above the sea; they are often several leagues in diameter; they are generally very shallow, but there is a deep one in a quartz-rock formation near C. Blanco. In the wet season, the whole, or a part, of the salt is dissolved, being redeposited during the succeeding dry season.
Elytron of Buprestis? The slate of Stonesfield has been shown by Mr. Lonsdale to lie at the base of the Great Oolite. It contains some pebbles of a rock very similar to itself, and which may be portions of the deposit, broken up on a shore at low water or during storms, and redeposited.
The President of the British Association, in his opening speech at the meeting of 1860, affirms the immense antiquity of these flint implements, and remarks: "At Menchecourt, in the suburbs of Abbeville, a nearly entire skeleton of the Siberian rhinoceros is said to have been taken out about forty years ago, a fact affording an answer to the question often raised, as to whether the bones of the extinct mammalia could have been washed out of an older alluvium into a newer one, and so redeposited and mingled with the relics of human workmanship.
It thus appears that the system lacks $300,000 a year of paying interest and expenses. It is estimated, however, that when the deposits have reached the sum Of $50,000,000, which at the present rate they soon will do, the system will be self-sustaining. By law the postal savings funds deposited at each post office are required to be redeposited in local banks.
Rock crushing develops heat, and allows a freer circulation of heated waters and vapors. Thus chemical reactions are greatly quickened; minerals are dissolved and redeposited in new positions, or their chemical constituents may recombine in new minerals, entirely changing the nature of the rock, as when, for example, feldspar recrystallizes as quartz and mica.
Iron ore, tin, copper and tungsten are extracted from the earth, refined, put to some use or wasted as the case may be, but they are gone. They may be replaced by other minerals. Through geological ages they may redeposited in the earth's crust. But to all intents and purposes, they are finished.
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