Feb. 1848. TEMPERATURE OF PLANTS. 37 



and consequent activity in the circulation. Its exposed 

 leaves maintained a temperature of 80°, nearly 25° cooler 

 than the similarly exposed sand and alluvium. On the 

 same night the leaves were cooled down to 54°, when 

 the sand had cooled to 51°. Before daylight the following 

 morning the sand had cooled to 43°, and the leaves 

 of the Calotropis to 4 5^°. I omitted to observe the 

 temperature of the sap at' the latter time ; but the sand at 

 the same depth (1 5 inches) as that at which its temperature 

 and that of the plant agreed at mid-day, was 68°. And 

 assuming this to be the heat of the plant, we find that 

 the leaves are heated by solar radiation during the day 8°, 

 and cooled by nocturnal radiation, 22^°. 



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 corre- 

 sponding 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 



