Nor need we say much in answer to our question,—“Why the ability to predict, as in the Australian case,” or generally to draw such conclusions and offer such suggestions and explanations, has remained so long unanswered, or been so lately acquired? Geology and chemistry are both young sciences, almost unknown till within a few years, rapidly advancing, and every day applying themselves more widely and directly to those subjects which effect the material prosperity and individual comforts of mankind. Knowledge which was not possessed before our day, could obviously neither be applied at all by ancient nations, nor earlier by the moderns. To the consideration of the absolute extent and probable productive durability of the gold regions newly brought to light—of their extent and richness compared with those known in former times—and of their probable effects on the social and financial relations of mankind, we shall now turn our attention. In the preceding part we have explained the circumstances in which gold occurs—the geological conditions which appear to be necessary to its occurrence—and where, therefore, we may expect to find it. But no conditions chemical or geological at present known are able to indicate—_a priori_, and apart from personal examination and trial—in what quantity the precious metal is likely to occur, either in the living rocks of a gold-bearing district, or in the sands and gravels by which it may be covered. Yet, next to the fact of the existence of gold in a country, the quantity in which it is likely to occur, and the length of time during which a profitable yield may be obtained, are the questions which most interest, not only individuals on the spot, but all other countries to which the produce of its mines is usually sent, or from which adventurers are likely to proceed. We have already remarked, that, in nearly all the gold regions which have been celebrated in past times, their mineral riches have been for the most part extracted from the drifted sands and gravels which overspread the surface. We have also drawn attention to the small amount of skill and intelligence which this extraction requires, and to the brief time in which such washings may be exhausted even by ignorant people. Most of our modern gold mines are situated in similar drifts. We may instance, from among the less generally known, those of Africa, from which are drawn the supplies that come to us yearly from the gold coast.