This accumulation of loose gold near the surface of auriferous veins, set at liberty from its matrix by the decomposition of the ore, and concentrated by degradation, is probably the reason of the great richness of many of what are called the "caps" of quartz veins; that is, the parts next the existing surface, and has also, perhaps, originated the belief that auriferous lodes deteriorate in value in depth. I at one time, after having studied the auriferous quartz veins of Australia, advocated this theory, which was first insisted upon by Sir R.I. Murchison, but further experience in North Wales, Nova Scotia, Brazil, and Central America has led me to doubt its correctness, excepting in cases such as we have been considering, where there has been an accumulation of gold in the superficial portions of lodes since their original formation. Gold is distributed in quartz veins in bands, and in patches of richer stone of more or less extent. These richer portions of the lodes, if sunk upon perpendicularly, will be passed through, but so also they would be if followed horizontally, their extent in one direction being as great as it is in the other. The chances of meeting with further patches of rich ore in depth, after one has been passed through, are about the same as they are in driving horizontally, and the frequency therefore with which the auriferous ores are met with along the surface will, as a rule, be an index of their occurrence in depth, if we be careful in distinguishing deposits belonging to the original condition of the lodes, and those due to subsequent concentration. To do this we must get below the immediate surface, and take as our guide the gold occurring in the solid undecomposed quartz, and not the loose grains contained in the fissures and cavities. (PLATE 7. SECTION OF MINE SHOWING METHOD OF EXTRACTING THE ORE. SECTION OF GOLD MINE. Diagram showing method of excavating ore at Santo Domingo Mines. A, Levels. B, Rise, down which the ore is thrown. D, Stopes. C, Stopes refilled with clay and barren rock. Lowest level, Tramway to Stamps.)