364 METEOROLOGY OF SOANE VALLEY. Appendix A. 



decidedly from that of the hills. In the valley dew is constantly 

 formed, which is owing to the amount of moisture in the air, for 

 nocturnal radiation is more powerful on the hills. The sunrise and 

 9 p.m. observations in the valley, give a mean depression of the dew- 

 point below the air of 12 0, 3, and those at the upper level of 21°-2, 

 with no dew on the hills and a copious deposit in the valley. The 

 corresponding state of the atmosphere as to saturation is 0*480 on 

 the hills and 0626 in the valley. 



The vegetation of the Soane valley is exposed to a less extreme 

 temperature than that of the hills ; the difference between solar 

 and nocturnal radiation amounting here only to 80 o, 5, and on the 

 hills to 96° - 5. There is no material difference in the power of the 

 sun's rays at the upper and lower levels, as expressed by the black- 

 bulb thermometer, the average rise of which above one placed in the 

 shade, amounted to 48° in both cases, and the maximum occurred 

 about 11 a.m. The decrease of the power of the sun's rays in the 

 afternoon is much the most rapid in the valley, coinciding with a 

 greater reduction of the elasticity of vapour and of humidity in the 

 atmosphere. 



The photometer observations show a greater degree of sun's light 

 on the hills than below, but there is not at either station a decided 

 relation between the indications of this instrument and the black- 

 bulb thermometer. From observations taken elsewhere, I am inclined 

 to attribute the excess of solar light on the hills to their elevation ; 

 for at a far greater elevation I have met with much stronger solar 

 light, in a very damp atmosphere, than I ever experienced in the 

 drier plains of India. In a damp climate the greatest intensity may 

 be expected in the forenoon, when the vapour is diffused near the 

 earth's surface ; in the afternoon the lower strata of atmosphere are 

 drier, but the vapour is condensed into clouds aloft which more 

 effectually obstruct the sun's rays. On the Birbhoom and Behar 

 hills, where the amount of vapour is so small that the afternoon 

 is but little drier than the forenoon, there is little difference 

 between the solar light at -each time. In the Soane valley again, 

 where a great deal of humidity is removed from the earth's 

 surface and suspended aloft, the obstruction of the sun's light is 

 very marked. 



