North-west of Hsia-hua-yüan, for a considerable distance, horizontal strata of purple shale and sandstone occur. These next give place to limestone, which extends to within six miles of Kalgan, when it is replaced by the volcanic rocks of the Kalgan district. In our rambles through the hills round this town we found porphyry, chiefly of a brown or brick-red colour, and other volcanic rock in great confusion. Specimens of serpentine and metamorphosed felspathic rocks were also obtained. To the north-west, basalt is exposed in the deep cutting of the stream bed, which ends in the Han-nor-pa pass. Further up this valley extensive beds of volcanic ash occur, which at first sight might be mistaken for the sedimentary rocks of the Shansi formations. The deposits are of a bright red colour, and in places assume the form of conglomerates, with large well-rounded boulders. This suggests that these beds were laid under water. Nearer the pass, these deposits are much lighter in colour, being pink or buff and light blue-grey. In places the original substance has degenerated into soft clay, while, wherever the strata assume the form of conglomerate, the fragments of harder rock are rough-edged and not rounded as they are nearer Kalgan. Beyond these beds basalt occurs right up to and beyond the Han-nor-pa pass. PART 5 THE GEOLOGY OF THE CH’ING HO AND HSI-WAN-TZŬ DISTRICT, NORTHERN CHIHLI Leaving Kalgan we travelled northward up the valley of the P’an-chang Ho for about six miles. The sides of this valley are steep and composed entirely of outcrops of trachyte of a mauve grey colour. This colour on the exposed surface is changed, through weathering, to a dark brown. Typical crystals of felspar occur throughout the mass. In the specimens gathered the crystals had undergone considerable decomposition. At a place called Hsi-tien-tzŭ the valley takes a bend eastward, at right angles to its original course, while a wide but waterless valley enters it from the north. This is called Ching-kou, while the main valley, which has a good permanent stream, is now called Ch’ing Ho. The trachyte continues all the way to Kao-chia-yin-tzŭ, just beyond which place it ends. Here it is of a lighter colour, the weathered surface being of a bright brick red, while the new fracture shows the rock itself to be of a light mauve-grey. The white crystals of felspar are also much larger and more noticeable than in the outcrops nearer Kalgan. Where they are exposed at the surface, these crystals rapidly disintegrate and are washed away, leaving the surface rock full of holes, which gives it something the appearance of a rock charged with air-bubbles. Beyond Kao-chia-yin-tzŭ, still working eastward, we found metamorphic (chiefly gneiss) rocks, alternating with plutonic (granite), the former predominating. Both the metamorphic and plutonic rocks are seamed with stringers, leads and ledges of quartz (probably auriferous).