On July 24th the expedition crossed the Khamba La and descended to the broad green valley of the Tsangpo. The crossing of that river, a work of real difficulty, was made tragic by the death of Major Bretherton, the brilliant transport officer, to whom, perhaps, more than to any other soldier, the military success in the enterprise was due. Not the least of the mysteries of Tibet was this secret stream, which the traveller, after miles of bleak upland, finds flowing among English woods and meadows. In Assam and Bengal it was the Brahmaputra; but when it entered the hills it was as unknown to civilized man as Alph or the Four Rivers of Eden. What its middle course was like and how it broke through the mountain barrier were questions which no one had answered,* nor at the time was there any accurate knowledge of its upper valleys. * See Chapter II. Once on the north bank Lhasa was but a short way off, and in growing excitement the expedition covered the last stages. It was one of the great moments of life, and we can all understand and envy the final hurried miles, till through the haze the eye caught the gleam of golden roofs and white terraces. The first prospect brought no disappointment. If the streets were squalid, they were set in a green plain seamed with waters; trees and gardens were everywhere; while, above, the huge Assisi-like citadel of the Potala typified the massive secrecy of generations, and the ring of dark hills reminded the onlooker that this garden ground was planted on the roof of the world. Meanwhile the expedition set itself down outside the gates to abide the pleasure of the sullen and perturbed masters. The deity of the place had gone on a journey, no one quite knew whither. He had kept his moonlight flitting a secret, and had gone off on the northern road with Dorjieff and a small escort to claim the hospitality of his spiritual brother of Urga. He had played his impossible game with spirit and subtlety, and he had a pretty taste for romance in its ending. "When one looks for mystery in Lhasa," wrote Mr. Candler, "one's thoughts dwell solely on the Dalai Lama and the Potala. I cannot help dwelling on the flight of the thirteenth incarnation. It plunges us into mediævalism. To my mind there is no picture so engrossing in modern history as that exodus when the spiritual head of the Buddhist Church, the temporal ruler of six millions, stole out of his palace by night, and was borne away in his palanquin."