The natural orders whose rarity is most noticeable, are Cruciferae, represented by only three kinds, and Caryophylleae. Of Ranunculaceae, there are six or seven species of Clematis, two of Anemone, one Delphinium, three of Thalictrum, and two Ranunculi. Compsitae and Leguminosae are far more numerous than in Sikkim.
The climate of Khasia is remarkable for the excessive rain-fall. Attention was first drawn to this by Mr. Yule, who stated, that in the month of August, 1841, 264 inches fell, or twenty-two feet; and that during five successive days, thirty inches fell in every twenty-four hours! Dr. Thomson and I also recorded thirty inches in one day and night, and during the seven months of our stay, upwards of 500 inches fell, so that the total annual fall perhaps greatly exceeded 600 inches, or fifty feet, which has been registered in succeeding years! From April, 1849, to April, 1850, 502 inches (forty-two feet) fell. This unparalleled amount is attributable to the abruptness of the mountains which face the Bay of Bengal, from which they are separated by 200 miles of Jheels and Sunderbunds.
This fall is very local: at Silhet, not thirty miles further south, it is under 100 inches; at Gowahatty, north of the Khasia in Assam, it is about 80; and even on the hills, twenty miles inland from Churra itself, the fall is reduced to 200. At the Churra station, the distribution of the rain is very local; my gauges, though registering the same amount when placed beside a good one in the station; when removed half a mile, received a widely different quantity, though the different gauges gave nearly the same mean amount at the end of each whole month.
The direct effect of this deluge is to raise the little streams about Churra fourteen feet in as many hours, and to inundate the whole flat; from which, however, the natural drainage is so complete, as to render a tract, which in such a climate and latitude should be clothed with exuberant forest, so sterile, that no tree finds support, and there is no soil for cultivation of any kind whatsoever, not even of rice. Owing, however, to the hardness of the horizontally stratified sandstone, the streams have not cut deep channels, nor have the cataracts worked far back into the cliffs. The limestone alone seems to suffer, and the turbid streams from it prove how rapidly it is becoming denuded. The great mounds of angular gravel on the Churra flat, are perhaps the remains of an extensive deposit, fifty feet thick, elsewhere washed away by these rains; and I have remarked traces of the same over many slopes of the hills around.
The mean temperature of Churra (elev. 4000 feet) is about 66 degrees, or 16 degrees below that of Calcutta; which, allowing for 22 degrees of northing, gives 1 degree of temperature to every 290 to 300 feet of ascent. In summer the thermometer often rises to 88 degrees and 90 degrees; and in the winter, owing to the intense radiation, hoar-frost is frequent. Such a climate is no less inimical to the cultivation of plants, than is the wretched soil: of this we saw marked instances in the gardens of two of the resident officers, Lieutenants Raban and Cave, to whom we were indebted for the greatest kindness and hospitality. These gentlemen are indefatigable horticulturists, and took a zealous interest in our pursuits, accompanying us in our excursions, enriching our collections in many ways, and keeping an eye to them and to our plant-driers during our absence from the station. In their gardens the soil had to be brought from a considerable distance, and dressed copiously with vegetable matter. Bamboo clumps were planted for shelter within walls, and native shrubs, rhododendrons, etc., introduced. Many Orchideae throve well on the branches of the stunted trees which they had planted, and some superb kinds of Hedychium in the ground; but a very few English garden plants throve in the flower-beds. Even in pots and frames, geraniums, etc., would rot, from the rarity of sunshine, which is as prejudicial as the damp and exposure. Still many wild shrubs of great interest and beauty flourished, and some European ones succeeded with skill and management; as geraniums, Salvia, Petunia, nasturtium, chrysanthemum, Kennedya rubicunda, Maurandya, and Fuchsia. The daisy seed sent from England as double, came up very poor and single. Dahlias do not thrive, nor double balsams. Now they have erected small but airy green-houses, and sunlight is the only desideratum.
At the end of June, we started for the northern or Assam face of the mountains. The road runs between the extensive and populous native village, or poonji, on the left, and a deep valley on the right, and commands a beautiful view of more waterfalls. Beyond this it ascends steeply, and the sandstone on the road itself is curiously divided into parallelograms, like hollow bricks,* [I have seen similar bricks in the sandstones of the coal-districts of Yorkshire; they are very puzzling, and are probably due to some very obscure crystalline action analogous to jointing and cleavage.] enclosing irregularly shaped nodules, while in other places it looks as if it had been run or fused: spherical concretions of sand, coloured concentrically by infiltration, are common in it, which have been regarded as seeds, shells, etc.; it also contained spheres of iron pyrites. The general appearance of much of this rock is as if it had been bored by Teredines (ship worms), but I never detected any trace of fossils. It is often beautifully ripple-marked, and in some places much honeycombed, and full of shales and narrow seams of coal, resting on a white under-clay full of root-fibres, like those of Stigmaria.
At about 5000 feet the country is very open and bare, the ridges being so uniform and flat-topped, that the broad valleys they divide are hidden till their precipitous edges are reached; and the eye wanders far east and west over a desolate level grassy country, unbroken, save by the curious flat-topped hills I have described as belonging to the limestone formation, which lie to the south-west. These features continue for eight miles, when a sudden descent of 600 or 700 feet, leads into the valley of the Kala-panee (Black water) river, where there is a very dark and damp bungalow, which proved a very great accommodation to us.* [It may be of use to the future botanist in this country to mention a small wood on the right of this road, near the village of Surureem, as an excellent botanical station: the trees are chiefly Rhododendron arboreum, figs, oaks, laurels, magnolias, and chestnuts, on whose limbs are a profusion of Orchideae, and amongst which a Rattan palm occurs.
Lailang-kot is another village full of iron forges, from a height near which a splendid view is obtained over the Churra flat. A few old and very stunted shrubs of laurel and Symplocos grow on its bleak surface, and these are often sunk from one to three feet in a well in the horizontally stratified sandstone. I could only account for this by supposing it to arise from the drip from the trees, and if so, it is a wonderful instance of the wearing effects of water, and of the great age which small bushes sometimes attain.
The vegetation is more alpine at Kala-panee (elevation, 5,300 feet); Benthamia, Kadsura, Stauntonia, Illicium, Actinidia, Helwingia, Corylopsis, and berberry—all Japan and Chinese, and most of them Dorjiling genera—appear here, with the English yew, two rhododendrons, and Bucklandia. There are no large trees, but a bright green jungle of small ones and bushes, many of which are very rare and curious. Luculia Pinceana makes a gorgeous show here in October.
The sandstone to the east of Kala-panee is capped by some beds, forty feet thick, of conglomerate worn into cliffs; these are the remains of a very extensive horizontally stratified formation, now all but entirely denuded. In the valley itself, the sandstone alternates with alum shales, which rest on a bed of quartz conglomerate, and the latter on black greenstone. In the bed of the river, whose waters are beautifully clear, are hornstone rocks, dipping north-east, and striking north-west. Beyond the Kalapanee the road ascends about 600 feet, and is well quarried in hard greenstone; and passing through a narrow gap of conglomerate rock,* [Formed of rolled masses of greenstone and sandstone, united by a white and yellow cement.] enters a shallow, wild, and beautiful valley, through which it runs for several miles. The hills on either side are of greenstone capped by tabular sandstone, immense masses of which have been precipitated on the floor of the valley, producing a singularly wild and picturesque scene. In the gloom of the evening it is not difficult for a fertile imagination to fancy castles and cities cresting the heights above.* [Hydrangea grows here, with ivy, Mussoenda, Pyrua, willow, Viburnum, Parnassia, Anemone, Leycesteria formosa, Neillia, Rubus, Astilbe, rose, Panax, apple, Bucklandia, Daphne, pepper, Scindapsus, Pierix, holly, Lilium giganteum ("Kalang tatti," Khas.), Camellia, Elaeocarpus, Buddleia, etc. Large bees' nests hang from the rocks.]