EAST NEPAL AND THE SIKKIM HIMALAYA MOUNTAINS. 107 



cloudy part of the day, and the fogs that obstruct the sun's rays 

 afterwards being both denser and of much greater perpendicular 

 height than is supposed usual with this phenomenon. Cloudless 

 afternoons are very rare in any month, and quite unknown during 

 the warm ones, so that the mean yearly temperatures of 10 a.m. 

 and 4 p.m. coincide within half a degree (10 a.m. o6"2°, 4 p.m. 

 56*7°), differing as much as 2° in the month of February only. 

 In the cold weather, again, the maximum occurs in the afternoon. 

 The mean temperature of the year coincides nearly with the 

 8 A.M. temperature, as far as I can ascertain. 



My own observations were taken hourly at Darjiling, for, on 

 the average, 18 hours of the day, during the rainy season of 

 1848, with many breaks however. From the end of October, 

 1848, to the latter part of January, 1849, I was travelling in 

 East Nepal and in Sikkira between the elevations of 4000 and 

 17,000 feet. January, February, and April of 1849 I speiit 

 near Darjiling ; March on the plains at the foot of the hills. 

 From the beginning of May till Christmas, 1849, was wliolly 

 spent in travelling at all elevations above 4000 feet, but cliiefly 

 in regions above 6000 feet, and for several months between 

 12,000 and 14,000 feet ; during September at 15,400 feet, and 

 in October I spent a few days at 16,700 to 17,000 feet. The 

 spring of 1850 (January to May) was passed in and about Dar- 

 jiling. During all these excursions I made the study of climate 

 second alone to botany. I recorded observations at certain 

 hours, which were those adopted at the Calcutta Observatory (5^ 

 due south of Sikkira), and at many of which Jiours my friend, 

 J. Muller, Esq., made comparative observations of pressure, tem- 

 perature, and wet-bulb at Darjiling, My first proceeding, after 

 halting or camping, was to hang the instruments in a very acces- 

 sible place screened from radiation ; and I endeavoured to observe 

 hourly, when at liberty to do so ; isolated observations in such 

 circumstances being generally useless. I have taken the results 

 of the comparison of a multitude of such observations, with 

 coincident ones at Calcutta and Darjiling, as the basis of my 

 calculations for the temperature, &c., of tiie zones above 7000 

 feet, checking them by various methods that suggested them- 

 selves. The computations in many cases are excessively com- 

 plicated and laborious, but during my stay in Sikkim I was 

 materially assisted in this, as well as in the preliminary calculation 

 of several hundred altitudes by barometer, by Mr. Muller, the 

 experienced accountant of the Calcutta Mint, to whose friendship 

 I am very largely indebted, and but for whose generous aid and 

 encouragement I should perhaps never have undertaken the 

 distracting task of working out general results from the materials 

 I accumulated. These broken series of comparative observations 



