2 p.m. Surface 104 degrees 22.5 inches 93 degrees 5 inches 88 degrees Sand at this depth 78 degrees. 5 a.m. Surface 51 degrees 28 inches 68 degrees Finding the fresh milky juice of _Calotropis_ to be only 72 degrees, I was curious to ascertain at what depth this temperature was to be obtained in the sand of the river-bed, where the plant grew. Surface 104.5 degrees, 1 inch 102 degrees, 2 inches 94 degrees, 2.5 inches 90 degrees, 3.5 inches 85 degrees (Compact), 8 inches 73 degrees (Wet), 15 inches 72 degrees (Wet). 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.