It rises near and drains the plains of Tingri and Khamba, and then turning due South, forces its way through the main chain of the Himalaya directly between the mountain passes of the Everest group on the one side, and of the Kanchengjanga group on the other. Between our camp at Kharta and the village of Kyamathang, which is on the actual Nepal frontier, a distance of some 20 miles, the river drops a vertical height of 4,000 feet; and therefore we were particularly interested in the exploration of this wonderful gorge, and we wished to find out, if we could, whether this tremendous vertical drop consisted of a series of great rapids and waterfalls or a steady fall in the bed of the river. It was also clear, from first glimpses that we had had of the Arun Gorge, that lower down they must be of the greatest possible grandeur and interest. I have before described how we looked down from our picnic into the Arun and hoped we should be able to explore it. When we despatched Noel and Morris it was in terribly bad weather, the whole of the Lower Kama being a smother of mist and the jungle dripping with moisture. We had most of us been down as far as a place called Chotromo, where the river is crossed by the road which leads up to the Popti La, and this is the common road down into Nepal. From there the road is far less well known, and is not so well marked. I will now give Noel’s description of his journey. [Illustration: FORDING THE BHONG CHU. ] “On the evening of the 27th June, at the end of our first day’s march, we pitched our camp on a little pleasant grassy shelf situated in a small clearing in the forest near empty shepherd huts, which comprise the camp at Chotromo. The hot, damp atmosphere of the Ka(r)ma here at 9,000 feet harbours a world of insect life. No sooner had the sun set that evening than swarms of tiny midges emerged. They annoyed us for most of the night, except when, in moments of exasperation, we got out of bed and drove them away by lighting a small fire of juniper-wood at the mouth of our tent. From Chotromo a little shepherd track leads down the left bank of the river to Kyamathang. In actual distance Kyamathang is not far, but the road is scarcely level for more than a few yards. It zigzags precipitously a thousand feet up and down in order to avoid the ravines through which the river rushes, thus trebling the marching distance. The forest here becomes more tropical; bamboos and ferns are thick in the undergrowth, the trees increase enormously in size, and leeches make their appearance. The path where it descends to the river passes through bog and marsh, where the Nepalese shepherds, who mostly use this road, in order to reach the upper grazing grounds, have cut and laid tree-trunks along the path. The forest here darkens owing to the height of the trees, junipers being particularly noticeable; most of the trees being festooned with thick grey lichen. Here and there on level