378 Observations made on a Botanical Excursion. [Oct. 



and on these hills 38°, the corresponding saturation points being 0.559 

 and 0.380. 



The differences between sunrise, forenoon and afternoon dew points 

 at Calcutta and on the hills, are 13°. 6 at each observation ; but the atmo- 

 sphere at Calcutta is proportionably drier in the afternoon than at sun- 

 rise, than it is on the hills : the difference between the Calcutta sunrise 

 and afternoon saturation point being 0.449 : and the hill sunrise and 

 afternoon, 0.190. The march of the dew point is thus the same in both 

 instances, but owing to the much higher temperature of Calcutta, and 

 greatly increased tension of the vapor, there the saturation points answer- 

 ing to these dew point temperatures, are very different. 



In other words, the atmosphere of Calcutta is loaded with moisture 

 in the early morning of this season, and is comparatively dry in the 

 afternoon ; in the hills again, it is scarcely more humid at sunrise 

 than at 3 p. m. That this dryness of the hills is partly due to eleva- 

 tion appears from the disproportionately moister state of the atmo- 

 sphere below the Dunwah pass. 



A retrospect of the ground passed over is unsatisfactory, as far as 

 botany is concerned, except as showing how potent are the effects of a 

 dry soil and climate, upon a vegetation which has no desert types. At 

 another season, probably many more species would be obtained, for of 

 annuals I scarce got a score of species. In a geographical point of 

 view the range of hills is exceedingly interesting, as being the N. E. 

 continuation of a chain which crosses the broadest part of the Penin- 

 sula, from the gulf of Cambay to the junction of the Ganges and 

 Hooghly at Rajmahal. This range runs south of the Soane and Vin- 

 dhya, which it meets I believe at Omerkuntuk ; the granite of this and 

 the sandstone of the other, being then both overlain with trap. Fur- 

 ther west again, the ranges separate, the present still betraying a 

 nucleus of granite, forming the Satpur range, which divides the valley 

 of the Taptee from that of the Nerbudda. The southern is, though 

 the most difficult of definition, the longest of the two parallel ranges, 

 the Vindhya continued as the Kymaon, terminating abruptly at the 

 Fort of Chunar. The general and geological features of the two, 

 especially along their eastern course, are very different. This of gneiss, 

 hornblende-schists and granites, in various highly inclined beds, through 

 which granite hills are pushed, most of them low, but one culminating 



