442 Notes, chiefly Botanical, made during an [May, 



temperature of 50.7. In spite of the heavy rain and fog the dew 

 point was always below the temperature, with which I am somewhat 

 surprized, for more drenching weather could not well be. The mean 

 dew point was 50.3, and consequent humidity 0.973.* 



These observations, and those of the Barometer, were taken some 60 

 feet below the summit, to which I moved the instruments on the morn- 

 ing of the 28th. At a much more exposed spot, the results would 

 have differed no doubt. A Thermometer then sunk to the same depth 

 as that below, stood at 49.7 ; or one degree colder than 60 ft. lower 

 down. 



The summit of Tonglo, by my Barometrical observations, taken simul- 

 taneously with those of Calcutta, gives the height 10,078.3 ft. Col. 

 Waugh's, by Trigonometry, 10,079.4 ft., a marvellous instance of the 

 perfection to which these instruments are brought, and above all of the 

 accuracy of the tablesf from which the altitudes are deduced. I hope 

 shortly to have the honor of laying before the Society some proofs of 

 the accuracy with which elevations by the Barometer may be obtained, 

 together with some account of the most recent tables now in use, and 

 which are no less remarkable for their comprehensiveness than sim- 

 plicity. 



May 23rd. — We spent a few hours of alternate fog and sunshine on 

 the top of the mountain, vainly hoping for the most modest view. The 

 air, which was always foggy, was alternately cooled and heated, as it 

 blew over the trees, or the open space we occupied, sometimes varying 

 5° and 6° in £ hour. Whenever a lull occurred the fog was sensibly 

 heated by the sun's rays. 



The number of mosses, Hepaticce and Lichens, growing near and on 

 the summit, is very remarkable. There were various species of Ferns, 

 and a small Agaricus grew on decayed twigs ; Lichens infested the naked 

 branches of the Rose, Barberry and Cherry. The trunks of both (he 

 Rhododendrons, owing to their smooth papery bark, and the bamboo, 

 are remarkably free from Cryptogamic vegetation. 



Having partially dried the tent in the wind, we commenced the 



* As expressed by the quotient of the tension at the temperature of the dew 

 point divided by that of the air. 



f There are Bessel's Tables, translated by Col. Sabine, and published in the 



number of Taylor's Scientific Memoirs. 



