The power this plant exercises of maintaining a low temperature of 72 degrees, though the main portion which is subterraneous is surrounded by a soil heated to between 90 degrees and 104 degrees, is very remarkable, and no doubt proximately due to the rapidity of evaporation from the foliage, and consequent activity in the circulation. Its exposed leaves maintained a temperature of 80 degrees, nearly 25 degrees cooler than the similarly exposed sand and alluvium. On the same night the leaves were cooled down to 54 degrees, when the sand had cooled to 51 degrees. Before daylight the following morning the sand had cooled to 43 degrees, and the leaves of the Calotropis to 45.5 degrees. I omitted to observe the temperature of the sap at the latter time; but the sand at the same depth (15 inches) as that at which its temperature and that of the plant agreed at mid-day, was 68 degrees. And assuming this to be the heat of the plant, we find that the leaves are heated by solar radiation during the day 8 degrees, and cooled by nocturnal radiation, 22.5 degrees.
Mr. Theobald (my companion in this and many other rambles) pulled a lizard from a hole in the bank. Its throat was mottled with scales of brown and yellow. Three ticks had fastened on it, each of a size covering three or four scales: the first was yellow, corresponding with the yellow colour of the animal's belly, where it lodged, the second brown, from the lizard's head; but the third, which was clinging to the parti-coloured scales of the neck, had its body parti-coloured, the hues corresponding with the individual scales which they covered. The adaptation of the two first specimens in colour to the parts to which they adhered, is sufficiently remarkable; but the third case was most extraordinary.
During the night of the 14th of February, I observed a beautiful display, apparently of the Aurora borealis, an account of which will be found in the Appendix.
February 15.—Our passage through the Soane sands was very tedious, though accomplished in excellent style, the elephants pushing forward the heavy waggons of mining tools with their foreheads. The wheels were sometimes buried to the axles in sand, and the draught bullocks were rather in the way than otherwise.
The body of water over which we ferried, was not above 80 yards wide. In the rains, when the whole space of three miles is one rapid flood, 10 or 12 feet deep, charged with yellow sand, this river must present an imposing spectacle. I walked across the dry portion, observing the sand-waves, all ranged in one direction, perpendicular to that of the prevailing wind, accurately representing the undulations of the ocean, as seen from a mast-head or high cliff. As the sand was finer or coarser, so did the surface resemble a gentle ripple, or an ocean-swell. The progressive motion of the waves was curious, and caused by the lighter particles being blown over the ridges, and filling up the hollows to leeward. There were a few islets in the sand, a kind of oases of mud and clay, in laminae no thicker than paper, and these were at once denizened by various weeds. Some large spots were green with wheat and barley-crops, both suffering from smut.
We encamped close to the western shore, at the village of Dearee (alt. 330 feet); it marks the termination of the Kymore Hills, along whose S.E. bases our course now lay, as we here quitted the grand trunk road for a rarely visited country.
On the 16th we marched south up the river to Tilotho (alt. 395 feet), through a rich and highly cultivated country, covered with indigo, cotton, sugar-cane, safflower, castor-oil, poppy, and various grains. Dodders (Cuscuta) covered even tall trees with a golden web, and the Capparis acuminata was in full flower along the road side. Tilotho, a beautiful village, is situated in a superb grove of Mango, Banyan, Peepul, Tamarind, and Bassia. The Date or toddy-palm and fan-palm are very abundant and tall: each had a pot hung under the crown. The natives climb these trunks with a hoop or cord round the body and both ancles, and a bottle-gourd or other vessel hanging round the neck to receive the juice from the stock-bottle, in this aerial wine-cellar. These palms were so lofty that the climbers, as they paused in their ascent to gaze with wonder at our large retinue, resembled monkeys rather than men. Both trees yield a toddy, but in this district they stated that that from the Phoenix (Date) alone ferments, and is distilled; while in other parts of India, the Borassus (fan-palm) is chiefly employed. I walked to the hills, over a level cultivated country interspersed with occasional belts of low wood; in which the pensile nests of the weaver-bird were abundant, but generally hanging out of reach, in prickly Acacias.
The hills here present a straight precipitous wall of horizontally stratified sandstone, very like the rocks at the Cape of Good Hope, with occasionally a shallow valley, and a slope of debris at the base, densely clothed with dry jungle. The cliffs are about 1000 feet high, and the plants similar to those at the foot of Paras-nath, but stunted: I climbed to the top, the latter part by steps or ledges of sandstone. The summit was clothed with long grass, trees of Diospyros and Terminalia, and here and there the Boswellia. On the precipitous rocks the curious white-barked Sterculia foetida "flung its arms abroad," leafless, and looking as if blasted by lightning.
A hole was sunk here again for the thermometers, and, as usual, with great labour; the temperatures obtained were— Air. 9 p.m. 64.5 degrees 5.30 a.m. 58.5 degrees 4 feet 6 inches, under good shade of trees 9 p.m. 77 degrees 11 p.m. 76 degrees 5.30 a.m. 76 degrees
This is a very great rise (of 4 degrees) above any of those previously obtained, and certainly indicates a much higher mean temperature of the locality. I can only suppose it due to the radiation of heat from the long range of sandstone cliff, exposed to the south, which overlooks the flat whereon we were encamped, and which, though four or five miles off, forms a very important feature. The differences of temperature in the shade taken on this and the other side of the river are 2.75 degrees higher on this side.