drained by an emissary. It sent out a river, which flowed down to the Tso-ngombo and the Panggong-tso, and, as we shall see later on, won an outlet to the Indian Ocean. As a consequence of the diminished precipitation the Panggong-tso has been cut off from the Indus system and the same cause has severed the connection
between this new lake and the Panggong-tso. The clearest proof that this was a freshwater lake is the mollusc shells. The remains of vegetation preserved in the dried ridges suggest that Alg e and seaweed also existed in this lake. These little ridges or ribbings (upper ill. of fig. 147) form meandering black lines on the white
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