The Tibetan zone consists of an intensely folded succession of shales and limestones, with subordinate sandstone quartzites, the folds striking East-West and mainly lying over towards the South, showing that the movements which produced them came from the North.

The uppermost rocks consist of the Kampa system of Hayden, a great thickness of limestones, which, where the rocks have escaped alteration, yield an a.s.semblage of fossils which determine their age as Cretaceous and Eocene.

Below these is a monotonous succession of shales, practically unfossiliferous, with occasional quartzites and limestones representing the Upper and Middle Jura.s.sic with at the base beds probably belonging to the Lias.

These Jura.s.sic shales are by far the most conspicuous formation in this part of Tibet, being repeated many times in complicated folds.

The Cretaceous-Eocene limestones form comparatively narrow bands, occurring as compressed synclines caught up in the folded complex of Jura.s.sic shales.

Along the Southern border of the Tibetan zone, below the base of the Jura.s.sic shales, is a great thickness (2,000 feet-3,000 feet) of thinly bedded limestones in which the fossils have been destroyed and the rocks themselves converted over considerable areas into crystalline limestones and calc-gneisses containing tremolite, epidote, tourmaline, etc., but still retaining their original bedded structure in the banding of the altered rock.

The absence of determinable fossils makes it impossible to determine the age of these with certainty, but from their lithological character and position in the sequence, it is possible that they correspond with the Tso Lhamo limestone in Sikkim (Lias) and the Kioto limestone of the Zangskar range (Lower Jura.s.sic and Upper Trias).

The Himalayan and crystalline zone is essentially composed of foliated and banded biot.i.te-gneiss, usually garnetiferous, on which lie, at comparatively low angles and with a general Northerly dip, the above-mentioned calc-gneisses.

These occur most abundantly to the North and West of Everest, in the Keprak, Rongbu, Hlalung and Rebu Valleys. The group of high peaks to the North-west of Everest (overlooking the Khombu Pa.s.s) is made up of these and intrusive schorl granite, and it would seem that the precipitous North-western face and spurs of Everest are the same.

The Eastern and North-eastern valleys, Chongphu, Kharta and Kama, which are in general at a lower level than the North-western valleys, are excavated in the biot.i.te-gneiss. On the North-eastern face of Everest fresh snow was too abundant at the time of my visit to make out what the rocks were.

a.s.sociated with the limestones and calc-gneisses are quartzites and tourmaline-biot.i.te schists which probably represent the lowest portions of the shales immediately overlying the limestones.

It is probable that the biot.i.te-gneiss is an igneous rock intrusive in the calc-gneisses and schists, but this and many other puzzling features of the crystallines require more detailed study than I was able to give this year.

Both biot.i.te-gneiss and metamorphosed sedimentaries are crowded with d.y.k.es and sills, of all dimensions, of schorl granite or pegmat.i.te to such an extent that this granite is frequently the predominant rock. It is highly resistant to weathering and it is doubtless due to its presence in large amount that such comparatively soft rocks as the calc-gneisses take part in forming some of the highest summits.

In the same way the scattered peaks of over 20,000 feet on the watershed between the Arun and the Tsangpo owe their prominence to their being groups of veins of a very similar granite, differing in that it contains biot.i.te in place of schorl. Around these separate centres of intrusion are areoles of metamorphism in which the Jura.s.sic shales have been converted into slates and phyllites.

Economically the area traversed by the Expedition is devoid of interest.

Barring a little copper staining on a few boulders on moraines no traces of ore were seen.

APPENDIX IV

THE SCIENTIFIC EQUIPMENT

BY A. R. HINKS, F.R.S., Secretary of the Royal Geographical Society.

The most important scientific work of the first year's expedition should have been the study of the physiological effects of high alt.i.tude that Dr. Kellas had undertaken, with the support of Professor Haldane, F.R.S., and of the Oxygen Research Committee of the Department of Scientific and Industrial Research. In his work on Kamet in 1920, Dr. Kellas had tried, and provisionally decided against, the use of oxygen compressed in cylinders: but he laboured under the grave disadvantage that the light cylinders he hoped to obtain had been, after his departure for India, p.r.o.nounced unsafe; and the cylinders sent out were clearly too heavy for effective use in climbing. Dr. Kellas had therefore fallen back on the use of oxygen prepared from the reaction between water and oxylith in an apparatus which included a kind of gas mask. He was prepared also to make several difficult researches into the physiological processes of adaptation to low oxygen pressure; and some delicate apparatus was prepared and sent out to him by the Oxygen Research Committee. Unhappily these interesting and important enquiries came to nought, for there was no one competent to carry them on after his lamented death at Kampa Dzong; and the Expedition of 1922 was thereby deprived of much information that should have been at its disposal in studying the use of oxygen for the grand a.s.sault.

The scientific equipment for which the Mount Everest Committee were directly responsible was not ambitious: the Survey of India were responsible for the whole of the survey and brought their own equipment, which is described elsewhere in this book. It was necessary to provide the climbing party only with aneroids, compa.s.ses, reserve field-gla.s.ses, thermometers and cameras, with subsidiary apparatus for checking the aneroids at the base camps, and heavier cameras for work at lower levels.

The aneroids by Cary, Porter & Co. and by Short & Mason were constructed in pairs, to operate from 15,000 to 23,000, and 22,000 to 30,000 feet respectively. They seem to have performed well on the whole, and tests made at the National Physical Laboratory since their return show that they have changed very little; but it cannot be said that their performances were very effectively controlled in the field, for until late in the season there were no trigonometrical heights available, and the climbers had little opportunity in their rather isolated circ.u.mstances of employing their aneroids to the best advantage, for purely differential work. Nor is there much to be said as yet on the value of the shortened form of George mercurial barometer, to come into action only at 15,000 feet (Cary, Porter & Co.). These instruments will find effective use only in the second season, when the reference points of the trigonometrical survey will be available as fundamental data.

The climbers carried "Magnapole" compa.s.ses with luminous points, and sometimes a Mark VIII prismatic; these all worked well. The simpler compa.s.s is the more convenient for use on snow when goggles must be worn. A luminous liquid compa.s.s (Short & Mason) was found very useful on long reconnaissance rides.

For the record of temperatures in camps Messrs. Negretti & Zambra had made three small pairs of maximum and minimum thermometers in leather travelling cases. These suffered some casualties, by theft, or being accidentally left out in the sun; and the pattern has been repeated for the second year's work.

The heavier photographic equipment included an old and well-seasoned 7 5 Hare Camera, lent to the Expedition, but newly fitted by Messrs.

Dallmeyer with a Stigmatic lens of 9 inches focal length, a negative telephoto lens of 4 inches focal length giving enlargement up to 6 times, and a set of Wratten filters. With this camera Mr. Wollaston secured some of the finest pictures taken on the Expedition.

There were also two quarter-plate cameras for gla.s.s plates: a Sinclair Una camera fitted by Messrs. Dallmeyer with a Stigmatic lens of 5.3 inches focal length, and Adon telephoto lens; and a second Sinclair camera lent by Captain Noel.

One or the other of these two was used by Mr. Mallory at many of the high camps, and both the Hare 7 5 and the Sinclair quarter-plate went to the 22,500-foot camp at the Lhakpa La: doubtless the greatest height yet attained by so large a camera as the former. The princ.i.p.al difficulty with these cameras was unsteadiness in a heavy wind when the telephoto lens was in use: and the tripods have been strengthened and the lens supports stiffened before they go out again.

The plates were of two kinds: Imperial Special Rapid and Fine Grain slow. The latter were generally preferred, and could hardly have been better. The Imperial Dry Plate Company, who generously made and presented these plates to the Expedition, deserve special thanks for their skill and for their generosity.

The cameras which used films were a Panoram Kodak of 5 inches focal length, with films 12 4 inches; a No. 1 Autograph Kodak, and two Vest Pocket Kodaks, all three fitted with Cooke lenses by Messrs. Taylor, Taylor & Hobson. The Panoram Kodak was used very successfully by Colonel Howard-Bury, and the splendid series of panoramas is the most useful, if not quite the most beautiful, set of photographs brought home. The smaller cameras were used by the climbing party with many good results.

Finally it must be said that a large part of the best photographs were taken by Colonel Howard-Bury with his own 7 5 Kodak, and the results very generously placed at the disposal of the Committee.

All the instruments were examined and tested at the National Physical Laboratory, and the thanks of the Committee are due to the Director and his staff, who gave most valuable advice and a.s.sistance.