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Updated: June 12, 2025
I ascended a lofty hill, situated about a mile and a half to the west of our encampment, and found it composed of felspathic porphyry, with a greyish paste containing small crystals of felspar; but, in the bed of the river, the same rock was of a greenish colour, and contained a great number of pebbles of various rocks, giving it the aspect of a conglomerate; but recognisable by its crystals of felspar, and from its being connected with the rock of the hill.
Its summit was flat, rough, and rocky; at the distance of four miles from our camp it receded a little from the river, and there limestone was observed, crowded with fossils like that on the opposite side of the river. Two miles farther, the bed of the river was formed by a felspathic rock, with beautiful dendrites.
The country was improving, beautifully grassed, openly timbered, flat, or ridgy, or hilly; the ridges were covered with pebbles, the hills rocky. The rocks were baked sandstone, decomposed granite, and a dark, very hard conglomerate: the latter cropped out in the bed of the river where we encamped. Pebbles of felspathic porphyry were found in the river's bed.
Wallabies were very numerous between the cliffs of the felspathic rock; and the fine fig trees along the banks of the river were covered with ripe fruit. The river made a wide sweep round the left side of a large limestone hill, whilst a chain of deep basaltic water-holes continued on its right.
The bearing of the Trois Tetons was north 50 degrees west, and the direction of the central ridge of the Wind River Mountains south 39 degrees east. The summit rock was gneiss. Sienite and feldspar succeeded in our descent to the snow line, where we found a felspathic granite.
Hearing us speak of mosaic granite, a rock occurring in Woodbridge, to which we had given this name, from the checker-like arrangement of its felspathic ingredient, he concluded that we attributed its formation to the era of Moses, and asked Percival what evidence he had for such an opinion. Small blame to him, perhaps, for the blunder, but it seemed a very droll one to geologists.
The same series again appears amidst the Lower Silurian beds of Co. Louth, near Drogheda. Metamorphic Series presumably of Lower Silurian Age. If, as seems highly probable, the great metamorphic series of Donegal and Derry are the representatives in time of the Lower Silurian series, some of the great sheets of felspathic and hornblendic trap which they contain are referable to this epoch.
Descending, the rocks became more micaceous, with broad seams of pipe-clay, originating in decomposed beds of felspathic gneiss: the natives used this to whitewash and mortar their temples. I passed the monastery of Neongong, the monks of which were building a new temple; and came to bring me a large present. Below it is a pretty little lake, about 100 yards across, fringed with brushwood.
In Ayrshire, and in the western parts of Devonshire, beds of felspathic porphyry, felstone and ash are interstratified with strata believed to be of Permian age. In Devonshire these have only recently been recognised by Dr. Irving and the author as of Permian age, the strata consisting of beds of breccia, lying at the base of the New Red Sandstone.
The road, on its ascent to the second moraine, passed over an immense accumulation of glacial detritus at the mouth of the second lateral valley, entirely formed of angular fragments of gneiss and granite, loosely bound together by felspathic sand.
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