Five busy days were spent at Tingri developing and printing; and as the weather showed little sign of improvement, I decided to go on with Headquarters to Choebuk, in the Rongbuk Valley and work on that side, so as to make sure of completing the most important part, in the vicinity of Everest, and return to the Kyetr[=a]k Valley if there should be time. So on the 24th Colonel Bury and I left Tingri and reached Choebuk on the 25th, where we met Mallory and Bullock, just in from their reconnaissance of the North and North-west sides of Everest. A talk with them gave me some idea of the country, and the view from an 18,000-foot hill above Choebuk enabled me to make a plan of campaign: far more extensive, as always, than the weather eventually allowed. Colonel Bury, Mallory and Bullock had gone on to Kh[=a]rta on July 26; on the 27th I moved up the right bank of the Rongbuk Valley some 10 miles, to the monastery, above which I took a 20,000-foot station the next day. The weather was dreadful, but at 6 p.m. I got a round of photographs, which really turned out very well considering the time of day at which they were taken: it took me four and a half hours to get up this peak--fresh snow and scree--and although I had no glissades, only half an hour to come down. On the 27th I moved camp to a grassy hollow near the snout of the glacier--Mallory and Bullock's base--and next day occupied another hill overlooking the main glacier and valley, and looking up the side valley on the East, which joins the Dz[=a]kar Chu just below the glacier snout. The next three days were spent in establishing a light camp on the left bank of the East branch of the Rongbuk Glacier, about 3 miles from its snout, and taking a station on its left bank to overlook both the East and main glaciers. The Rongbuk Glacier is made up of two large branches, one flowing from the snow basin immediately below the great North wall of Everest, and the other, the "West Rongbuk" which joins the main stream about 4 miles above the snout of the glacier, flowing East in the basin between the high North-west ridge of Everest and the South-east slopes of Pk. 25,990 (Gy[=a]chung Kang). At one time there was a third branch, the "East Rongbuk," which must have also joined the main stream, but this has receded until its snout is now a mile or more East of the main glacier, and only its torrent pours into a large cave in the latter. The East Rongbuk itself consists of two branches: one, the more southerly, flows from the great snow basin (which we eventually crossed to reach the North Col) between Everest, its North Peak and Col, and Pk. 23,800 (Kh[=a]rtaphu); and the other, which joins the South branch about 2 miles from its snout, from between Pks. 23,800 and 23,420. The former gives a 20,000-foot pass, very steep on the South side, to the K[=a]ma Valley; and the latter, an easy pass of about the same height to the head of one branch of the Kh[=a]rta Valley.