ramparts. We ascertained subsequently, that on other parts of the lake-shore beach-lines run at a very appreciably higher elevation than the highest rampart at the beginning of the latitudinal valley. Accordingly I was surprised to find no other rampart preserved above this one in the valley itself, and all the more so when I remembered that the circular rampart which I have just described is the oldest of all and yet is the biggest, so that it has possessed sufficient power to withstand the destructive energy of the atmospheric forces and of disintegration. We must suppose therefore that the lake formerly thrust a deep bay into this latitudinal valley, which reached a long way above the highest of the still surviving ramparts, but that it did not maintain it sufficiently long at that altitude for it to be able to build up ramparts, and shape them, and leave them of the same dimensions as the big rampart. Either the lake fluctuated at that period, and so conspired to level the then existing latitudinal valley, or else it dropped so swiftly that the wave-movement was not able to build up ramparts strong enough to resist destruction. Finally, I would call attention to the more or less exposed position of the beginning of the latitudinal valley in relation to the deposition of sediment from off the neighbouring mountains. Camp CVII, which has an altitude of 4,821 m., belongs to a part of the latitudinal valley which under any circumstances lies considerably higher than even the highest of the beach-lines that I measured subsequently beside the Lakor-tso. It is about half-way between that camp and the lake-shore that we have to look for the point which lies at about the same level as the highest of the beach-lines which I measured, or 133 m. above the existing level of the lake. And from that point onwards I expected to find at any rate faint indications of beach-lines at the same level at which I measured them elsewhere. As a matter of fact however I did not find any. This may be in great part due to their having been levelled down, covered over, and gradually planed away by the solid material, the products of disintegration and sedimentation, which have been carried down by chance streams from off the slopes of the mountains to the north, and deposited in the lowest parts of the latitudinal valley. On the other hand, the southern range, in which we found such a great number of gullies and watercourses, was unable to make any contribution to the work of covering over, because all its tributaries terminate in the main stream of the valley, which brushes the foot of the range on that side. But why, it may be asked, have just these shore-ramparts been obliterated, whereas those which begin at the big sweeping curve are still in a good state of preservation ? The probable reason is, that just there the northern range inclines to the west-north-west, and between its continuation and the old bottom of the lake in the lowest part of our valley there stretches a small ridge, or rather a series of minor mountains, that are frequently interrupted and detached, but still fairly sharply outlined and craggy. These subsidiary mountains serve as a protecting wall against the streams which have 'flowed south off the slopes of the northern range, bringing with them detritus and sediment. Between the northern range and the subsidiary mountains on the northern shore of the lake runs the latitudinal valley in which Littledale travelled, thus leaving Lakor-tso to the south, although he saw the lake from his line of march and entered it correctly by name on his map. From this point therefore my route runs a good deal farther south than
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