A few of the Bhotan coolies having voluntarily returned, I left Tonglo on the 5th, and descended its west flank to the Mai, a feeder of the Myong. The descent was as abrupt as that on the east face, but through less dense forest; the Sikkim side (that facing the east) being much the dampest. I encamped at dark by a small village, (Jummanoo) at 4,360 feet, having descended 5000 feet in five hours. Hence we marched eastward to the village of Sakkiazung, which we reached on the third day, crossing _en route_ several spurs 4000 to 6000 feet high, from the same ridge, and as many rivers, which all fall into the Myong, and whose beds are elevated from 2,500 to 3000 feet. Though rich and fertile, the country is scantily populated, and coolies were procured with difficulty: I therefore sent back to Dorjiling all but absolute indispensables, and on the 9th of November started up the ridge in a northerly direction, taking the road from Ilam to Wallanchoon. The ascent was gradual, through a fine forest, full of horn-bills (_Buceros_), a bird resembling the Toucan ("Dhunass" Lepcha); at 7000 feet an oak (_Quercus semecarpifolia_), "Khasrou" of the Nepalese, commences, a tree which is common as far west as Kashmir, but which I never found in Sikkim, though it appears again in Bhotan.* [This oak ascends in the N.W. Himalaya to the highest limit of forest (12,000 feet). No oak in Sikkim attains a greater elevation than 10,000.] It forms a broad-headed tree, and has a very handsome appearance; its favourite locality is on grassy open shoulders of the mountains. It was accompanied by an _Astragalus, Geranium,_ and several other plants of the drier interior parts of Sikkim. Water is very scarce along the ridge; we walked fully eight miles without finding any, and were at length obliged to encamp at 8,350 feet by the only spring that we should be able to reach. With respect to drought, this ridge differs materially from Sikkim, where water abounds at all elevations; and the cause is obviously its position to the westward of the great ridge of Singalelah (including Tonglo) by which the S.W. currents are drained of their moisture. Here again, the east flank was much the dampest and most luxuriantly wooded. While my men encamped on a very narrow ridge, I ascended a rocky summit, composed of great blocks of gneiss, from which I obtained a superb view to the westward. Immediately below a fearfully sudden descent, ran the Daomy River, bounded on the opposite side by another parallel ridge of Sakkiazung, enclosing, with that on which I stood, a gulf from 6000 to 7000 feet deep, of wooded ridges, which, as it were, radiated outwards as they ascended upwards in rocky spurs to the pine-clad peaks around. To the south-west, in the extreme distance, were the boundless plains of India, upwards of 100 miles off, with the Cosi meandering through them like a silver thread.