And, first, as to the Geography of the question. There are no limits either in latitude or longitude, as used to be supposed, within which gold deposits are confined—none within which they are necessarily most abundant. In old times, the opinion was entertained that the precious metals favoured most the hot and equatorial regions of the earth. But the mines of Siberia, as far north as 69° of latitude, and the deposits of California, supposed to extend into Oregon, and even into Russian America, alone show the absurdity of this opinion. Nor does the physical character of a country determine in any degree whether or not it shall be productive of gold. It may, like California, border the sea, or be far inland, like the Ural slopes, or the Steppes of the Kirghis; it may be flat, and of little elevation, or it may abound in streams, in lakes, and in mountains;—none of these conditions are necessarily connected with washings or veins of gold. It is true that mountain chains are usually seen at no great distance from localities rich in golden sands, and that metalliferous veins often cut through the mountains themselves. But these circumstances are independent of the mountains as mere physical features. It is not because there are mountains in a country that it is rich in gold, else gold mines would be far more frequent; and mountainous regions, like our own northern counties, would abound in mineral wealth. It is the nature of the rocks of which a country consists—its geological and chemical characters, in other words, which determine the presence or absence of the most coveted of metals. Humboldt, indeed, supposed, from his observations, that, to be productive of gold, the chain of mountains which skirt the country must have a meridional direction. But further research has shown that this is by no means a necessary condition, although hitherto, perhaps, more gold has been met with in the neighbourhood of chains which have a prevailing north or south direction than of any other. We may safely say, therefore, that there are no known physical laws or conditions, by the application or presence of which the existence of gold can with any degree of probability be predicted. Let us study for a little, then, the geology of a region of gold. _First_, Every general reader now-a-days is aware that the crust of our globe consists of a series of beds of rock, laid one over the other, like the leaves of a book; and that of these the lowest layers, like the courses of stone in the wall of a building, are the oldest, or were the first laid down. These rocky beds are divided into three groups, of which the lowest, or oldest, is called the primary; the next in order, the secondary; and the uppermost, or newest, the tertiary.