Report on the agriculture and geology of MississippiEmbracing a sketch of the social and natural history of the state . systems, have beenomitted as not essential to the illustration. Although all the foregoing principal divisions or for-mations are found to exist in all the countries that havebeen geologically explored, it is not to be inferred thatall the strata of which they are composed pervade thewhole globe. Many of them, on the contrary, are absentin different countries, owing to the relative position ofthe earths surface, and the distribution of land andwater at the period of their dep
Report on the agriculture and geology of MississippiEmbracing a sketch of the social and natural history of the state . systems, have beenomitted as not essential to the illustration. Although all the foregoing principal divisions or for-mations are found to exist in all the countries that havebeen geologically explored, it is not to be inferred thatall the strata of which they are composed pervade thewhole globe. Many of them, on the contrary, are absentin different countries, owing to the relative position ofthe earths surface, and the distribution of land andwater at the period of their deposition. They are repre-sented, therefore, in the order they assume in point oftime, being governed by the mutations which the earthhas undergone, and the paroxysms of upheaval and sub-sidence, more or less active and general, which, at remoteand widely separated periods, have repeatedly occurred. But, although important strata, or even entire groups,may be missing or non-existent in some quarters, in noneis their relative order inverted or transposed; but theymaintain an undeviating succession consistent with the. GEOLOGY. 211 period of their formation; and thus it is that all mineralsare not to be found or expected alike in all situations, orwhere the strata to which they properly belong do notand cannot in the nature of things, exist. The thickness of all the strata taken collectively, asestimated on the section before referred to, Plate IX.,amounts to several miles. Now, as the deepest shaftyet sunk into the earth in mining operations is said notgreatly to exceed half a mile, it may be asked how it isthat geologists have arrived at a knowledge of so muchof the earths crust as they claim to have acquired ? If the different strata had remained undisturbed inthe position in which they were first deposited, we musthave remained forever ignorant, not only of the characterand thickness of these strata, but of their very exist-ence. But, in those great convulsions which the earthh
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