The broken-up and irregular western flank of the Rocky Mountains appears to be the true gold-bearing region of British Columbia. Gold has indeed been found in nearly every part of the colony where it has been looked for, but never in large quantities, except on the streams issuing from this district, as the Eraser and Columbia with their tributaries. It has been found also on the eastern slope, on the North Saskatchewan and Peace Rivers. But the amount obtained on the Saskatchewan has been inconsiderable; and it is worthy of remark that, while this river takes its rise just to the west of the middle line of the main ridge, Peace River, on which rich prospects have been discovered, has its origin fairly on the western side, flows through the auriferous tract for a considerable distance, and then turning east, passes through a wide rent in the Rocky Mountains. In crossing by the Yellow Head Pass, we met with carboniferous limestone, then Devonian, and near Robson’s Peak, on the western slope, saw for the first time the dark slates and schistose rocks, with veins of quartz-- probably of the upper Silurian strata--which mark the auriferous tract. West of this, an extensive region of what appears to be eruptive trap commences, and probably continues up to the Cascade, or coast range, to the westward; while to the south-east it stretches across the valleys of the Fraser and Thompson to that of the Columbia. The Cascade Range consists of granitic and plutonic rocks, and in places clay-slate and semi-crystalline limestones occur. The district of Cariboo is the richest portion of the British Columbian gold field, and here the geologic disturbance has been the greatest. Cariboo is a sea of mountains and pine-clad hills, the former rising to a height of 7,000 or 8,000 feet, surrounded by a confused congeries of the latter. Everywhere the surface has been disturbed, so that hardly a foot of level ground can be found, except at the bottom of the narrow gullies running between these hills. Strata are tilted on end, and beds of streams heaved up to the tops of hills. Round this centre of wealth poured up from the depths below, the main branch of the Fraser wraps itself in its semi-circular course, and has received from thence, by numerous tributaries, the gold found in its sands.