Road-mending is pretty general at this time of the year, and upon roads now being newly macadamized we may pick up a good many differing specimens of granite. On the newly-broken surface of one of them, four substances of which it is composed can be perceived with great distinctness. The more earthy-looking rock, in which the others seem to be embedded, is called felspar; the little hard white stones are bits of quartz; the dark specks are specks of hornblende, and the shining scales are mica. Felspar, quartz, hornblende, and mica are the four constituents of granite. These are among the rocks of the most ancient times, which form a complete barrier to the power of the geologist in turning back the pages which relate the story of our globe. Layer under layer--leaf behind leaf--we find printed the characters of life in all past ages, till at last we come to rocks--greenstone, porphyry, quartz, granite, and others--which contain no trace of life; which do not show, as rocks above them do, that they have been deposited by water; but which have a crystalline form, and set our minds to think of heat and pressure. These lowest rocks are frequently called "igneous," in contradistinction to the stratified rocks nearer the surface, which have been obviously deposited under water. Between the two there is not an abrupt transition; for above the igneous, and below the aqueous, are rocks which belong to the set above them, insomuch as they are stratified; while they belong to the set below them--insomuch as they are crystalline, contain no traces of life, and lead us by their characters to think of heat and pressure. These rocks, on account of their equivocal position, are called metamorphic. Under the influence of air, combined with that of water--water potent in streams, lakes, and seas, but not less potent as a vapor in our atmosphere, when aided by alternations in the temperature--granite decomposes. We noticed that one of the constituents of granite--felspar--was a comparatively earthy-looking mass, in which the other matters seemed to be embedded. In the decomposition of granite, this felspar is the first thing to give way; it becomes friable, and rains or rivers wash it down. Capital soil it makes. When the constituents of granite part in this way, quartz is the heaviest, and settles. Felspar and the others may run with the stream, more or less; quartz is not moved so easily. Now, as our neighbors in America would put it, "that's a fact;" and it concerns our gossip about gold.