8 Beport on the Magnetic Survey. [No. 1. 



made in localities of particular interest on account of their height, 

 Tonglo exceeding 10,000 ft., Phulloot nearly reaching 12,000 ft. 



The thermometer readings in the following tables are corrected 

 for the errors of the instruments, which had been most carefully 

 ascertained before our departure from Europe at the Kew Observa- 

 tory and examined during our stay in India every three or four 

 months. 



The readings of the barometer are reduced to the freezing point. 



The instruments for determining the temperature of the ground 

 were corrected of their index errors and also reduced to the true 

 temperature of the stratum in which the bulb of the instrument 

 stood, a correction instrument, containing only a capillary column of 

 mercury without a bulb, being immersed in the same stratum. 



In the following tables the variation is given for every full hour. 

 The direct observations included the time from 5 a. m. to 10 p. m. 

 Minima and maxima were also registered.* 



These observations were projected on a paper covered with square 

 millimeters, and the hourly changes for the hours without observa- 

 tions were read off from the curves traced out for every day. 



At Tonglo I left an observer after our departure, and the observa- 

 tions have thus been continued there from May to August without 

 interruption. 



* Sometimes observations were made, but not so regularly, at different hours of 

 the night. 



