56 FROM CENTRAL TIBET TO LADAK.
in which we detected a gentle current. It was not easy to account for the presence of this narrow tongue of sedimentary matter, for there seemed to be no reason at all why it should have originated in this sound. Possibly we might look upon it as a continuation, or the termination, of a branch of the third of the ranges on the island, although it does not indeed consist of hard rock, in fact it does not even consist of gravel. But its shape is altogether antagonistic to any such supposition; for its upper surface is perfectly level and its shores abrupt, not sloping gently down towards the lake. Moreover its breadth remains uniform throughout; nor does it exhibit any irregularities such as would suggest a former hilly ridge. The explanation which seemed to me to be the most likely, and on account of the
Fig. 39. VIEW FROM THE NARROW PASSAGE IN THE NAKTSONG-TSO.
relief of the immediate surroundings the most plausible, is this: that we have here at length a trace of a former moraine ridge, that has been left by an ice-stream which once flowed down through this sound. To this question I will however return after describing the rest of the sound. This regularly formed tongue of land does not, it is true, directly resemble an ordinary moraine, but almost seems like the work of human hands; but that may be a pure coincidence. Its summit may have been flattened by aqueous agency at a time when the lake-level stood a meter or a meter and a half higher than it does now. And equally whether the lake is drained by an underground channel or by some river connection that I did not see, it is but natural, and what might be expected, that its level should drop in consequence of the continuous erosion in the efferent channel, the effect being to bring the old moraine ridge above the water and expose it to the light of day. When the water covered it, its surface would be smoothed by the beat of the waves, but except for that the moraine would be protected against disintegration
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