[211] Sparganium ramosum, Eleocharis palustris, Scirpus triqueter, and Callitriche verna? Some very tropical genera ascend thus high; as Paspalum amongst grasses, and Scleria, a kind of sedge.
Below this I passed an extensive stalactitic deposit of lime, and a second occurred lower down, on the opposite side of the valley. The apparently total absence of limestone rocks in any part of Sikkim (for which I made careful search), renders these deposits, which are far from unfrequent, very curious. Can the limestone, which appears in Tibet, underlie the gneiss of Sikkim? We cannot venture to assume that these lime-charged streams, which in Sikkim burst from the steep flanks of narrow mountain spurs, at elevations between 1000 and 7000 feet, have any very remote or deep origin. If the limestone be not below the gneiss, it must either occur intercalated with it, or be the remains of a formation now all but denuded in Sikkim.
Terrific landslips had taken place along the valley, carrying down acres of rock, soil, and pine-forests, into the stream. I saw one from Kampo Samdong, on the opposite flank of the valley, which swept over 100 yards in breadth of forest. I looked in vain for any signs of scratching or scoring, at all comparable to that produced by glacial action. The bridge at the Tuktoong, mentioned at [p. 31,] being carried away, we had to ascend for 1000 feet (to a place where the river could be crossed) by a very precipitous path, and descend on the opposite side. In many places we had great difficulty in proceeding, the track being obliterated by the rains, torrents, and landslips. Along the flats, now covered with a dense rank vegetation, we waded ankle, and often knee, deep in mud, swarming with leeches; and instead of descending into the valley of the now too swollen Lachen, we made long detours, rounding spurs by canes and bamboos suspended from trees.
At Choongtam the rice-fields were flooded: and the whole flat was a marsh, covered with tropical grasses and weeds, and alive with insects, while the shrill cries of cicadas, frogs and birds, filled the air. Sand-flies, mosquitos, cockroaches, and enormous cockchafers,[[212]] Mantis, great locusts, grasshoppers, flying-bugs, crickets, ants, spiders, caterpillars, and leeches, were but a few of the pests that swarmed in my tent and made free with my bed. Great lazy butterflies floated through the air; Thecla and Hesperides skipped about, and the great Nymphalidæ darted around like swallows. The venomous black cobra was common, and we left the path with great caution, as it is a lazy reptile, and lies basking in the sun; many beautiful and harmless green snakes, four feet long, glided amongst the bushes. My dogs caught a “Rageu,”[[213]] a very remarkable animal, half goat and half deer; the flesh was good and tender, dark-coloured, and lean.
[212] Eucerris Griffithii, a magnificent species. Three very splendid insects of the outer ranges of Sikkim never occurred in the interior: these are a gigantic Curculio (Calandra) a wood-borer; a species of Goliath-beetle, Cheirotonus Macleaii, and a smaller species of the same rare family, Trigonophorus nepalensis; of these the former is very scarce, the latter extremely abundant, flying about at evenings; both are flower-feeders, eating honey and pollen. In the summer of 1848, the months at Dorjiling were well marked by the swarms of peculiar insects that appeared in inconceivable numbers; thus, April was marked by a great black Passalus, a beetle one-and-a-half inch long, that flies in the face and entangles itself in the hair; May, by stag-beetles and longicorns; June, by Coccinella (lady-birds), white moths, and flying-bugs; July, by a Dryptis? a long-necked carabideous insect; August, by myriads of earwigs, cockroaches, Goliath-beetles, and cicadas; September, by spiders.
[213] “Ragoah,” according to Hodgson: but it is not the Procapra picticaudata of Tibet.
I remained here till the 15th of August,[[214]] arranging my Lachen valley collections previous to starting for the Lachoong, whence I hoped to reach Tibet again by a different route, crossing the Donkia pass, and thence exploring the sources of the Teesta at the Cholamoo lakes.
[214] Though 5° further north, and 5,268 feet above the level of Calcutta, the mean temperature at Choongtam this month was only 12·5° cooler than at Calcutta; forty observations giving 1° Fahr. as equal to 690 feet of elevation; whereas in May the mean of twenty-seven observations gave 1° Fahr. as equal to 260 feet, the mean difference of temperature being then 25°. The mean maximum of the day was 80°, and was attained at 11 a.m., after which clouds formed, and the thermometer fell to 66° at sunset, and 56° at night. In my blanket tent the heat rose to upwards of 100° in calm weather. The afternoons were generally squally and rainy.
Whilst here I ascertained the velocity of the currents of the Lachen and Lachoong rivers. Both were torrents, than which none could be more rapid, short of becoming cataracts: the rains were at their height, and the melting of the snows at its maximum. I first measured several hundred yards along the banks of each river above the bridges, repeating this several times, as the rocks and jungle rendered it very difficult to do it accurately: then, sitting on the bridge, I timed floating masses of different materials and sizes that were thrown in at the upper point. I was surprised to find the velocity of the Lachen only nine miles per hour, for its waters seemed to shoot past with the speed of an arrow, but the floats showed the whole stream to be so troubled with local eddies and backwaters, that it took from forty-three to forty-eight seconds for each float to pass over 200 yards, as it was perpetually submerged by under-currents. The breadth of the river averaged sixty-eight feet, and the discharge was 4,420 cubic feet of water per second. The temperature was 57°.
At the Lachoong bridge the jungle was still denser, and the banks quite inaccessible in many places. The mean velocity was eight miles an hour, the breadth ninety-five feet, the depth about the same as that of the Lachen, giving a discharge of 5,700 cubic feet of water per second;[[215]] its temperature was also 57°. These streams retain an extraordinary velocity, for many miles upwards; the Lachen to its junction with the Zemu at 9000 feet, and the Zemu itself as far up as the Thlonok, at 10,000 feet, and the Lachoong to the village of that name, at 8000 feet: their united streams appear equally rapid till they become the Teesta at Singtam.[[216]]