difference of 14 degrees temperature, which is at the rate of
1 degree for every 347 feet of ascent.* [Forty-seven observations,
comparative with Calcutta, gave 34. degrees difference, and if 5.5
degrees of temperature be deducted for northing in latitude, the
result is 1 degree for every 412 feet of ascent. My observations at
the junction of the rivers alt. 10,850 feet), during the early part
of the mouth, gave 1 degree to 304 feet, as the result of twenty-four
observations with Dorjiling, and 1 degree to 394 feet, from
seventy-four observations with Calcutta.]

The temperature of these rivers varies extremely at different parts
of their course, depending on that of their affluents. The Teesta is
always cool in summer (where its bed is below 2000 feet), its
temperature being 20 degrees below that of the air; whereas in
mid-winter, when there is less cloud, and the snows are not melting,
it is only a few degrees colder than the air.* [During my sojourn at
Bhomsong in mid-winter of 1848 (see v. i. chapter xiii), the mean
temperature of the Teesta was 51 degrees, and of the air 52.3
degrees; at that elevation the river water rarely exceeds 60 degrees
at midsummer. Between 4000 feet and 300 (the plains) its mean
temperature varies about 10 degrees between January and July; at 6000
feet it varies from 55 degrees to 43 degrees during the same period;
and at 10,000 feet it freezes at the edges in winter and rises to 50
degrees in July.] At this season, in descending from 12,000 feet to
1000 feet, its temperature does not rise 10 degrees, though that of
the air rises 30 degrees or 40 degrees. It is a curious fact, that
the temperature of the northern feeders of the Teesta, in some parts
of their course, rises with the increasing elevation! Of this the
Zemu afforded a curious example: during my stay at its junction with
the Thlonok it was 46 degrees, or 6 degrees warmer than that river;