On 21st June they crossed a pass of over 13,000 feet into the valley of the river known as the Po-Tsangpo, an affluent of the Brahmaputra. It was a stream 80 yards wide, and of such rapidity that its current was one whirl of foam. The natives were in great fear of the Chinese, and it was necessary to go boldly to Showa, the capital, where a letter could be received from the Abor Survey party vouching for their respectability. The Chinese had burned the place, killed the chief, and decapitated the council, and the inhabitants looked askance at the travellers because of the Chinese writing on a tablet of Indian ink which they carried. After three days, however, a letter arrived from the Abor party, which persuaded them that Captain Bailey and Captain Morshead were at any rate servants of the English King. The explorers now moved north-eastwards down the Po-Tsangpo, finding great difficulty in crossing the tributaries, where the bridges had mostly been destroyed. It was a beautiful land, bright with primula, iris, and blue poppy, and the roads were lined with raspberries. They were now leaving the Po-me country and travelling among a more civilized type of Tibetan, who wore hats like clergymen, made out of yak's hair. After crossing a pass of over 15,000 feet they returned to the main stream of the Tsangpo. This country was under the charge of Tzongpen of Tsela, who came to meet the travellers--an urbane gentleman whose son was at Rugby and a promising cricketer. They were now on the Tsangpo above the mysterious gorges. They had left behind them the hot valleys of the lower stream and found a dry Tibetan dale, where the chief crops were barley and buckwheat. The river was broad and slow, at one point stretching into a lake 600 yards wide, and its altitude was 9,680 feet. The problem was now to follow it down from that point to the point of their last observation, where the altitude was only 2,610 feet. Somewhere in the intervening tract of gorge it must make the enormous descent of over 7,000 feet. The first stage was the twenty-two miles down to Gyala, which had been visited in 1878. The stream was in flood owing to melting snows, and the water-side track was difficult. Four days' march below Gyala they reached Pemakochung, the limit of Kinthup's exploration. So far they had passed various small rapids, but nothing in the nature of a fall. A mile below Pemakochung they came on Kinthup's cascade. It proved to be only some 30 feet high and not vertical.