58 Report on the Progress of the Magnetic Survey. [No. 1. 



In connexion with this fact it deserves mention, that in summer 

 the reverse takes place, and that the maximum heat of Central India, 

 at equal elevations, generally exceeds somewhat that of Southern 

 India. 



Together with the observations of the dry and wet bulb thermo- 

 meters, the readings of the barometer were registered, and I have 

 been able to determine the heights of all important places on the 

 route followed. Some stations were determined both by the baro- 

 meter and the boiling point thermometer, which from its minute 

 and accurate divisions (each degree of Celsius is divided into 100 

 parts) and having been carefully compared at different heights with 

 barometers, may be considered as giving equally accurate results with 

 the barometer itself. On the journey from Sohagpore to Rewah, 

 I used only this instrument, as the barometer was leaking very much, 

 and some air had introduced itself into it. 



The minimum of barometric pressure at about 4 p. m. occurred 

 on the small plateau of Umerkuntuk, very nearly at the same time 

 as in the lower valleys and plains of Hindustan, and the daily vari- 

 ation of the barometer seems to be very nearly the same at Umer- 

 kuntuk as it is in the plains. 



The temperature of the earth at different depths was determined 

 by the long thermometer (one metre in length.) For greater depths 

 I used a thermometer, the bulb of which was made extremely in- 

 sensible. The observations of the temperature of the ground at 

 Umerkuntuk, compared with similar data around the base of the 

 hill, afford some curious examples of the cooling influences which 

 extensive jungles have, upon the temperature of the ground. . At 

 Umerkuntuk the temperature was, 22nd to 25th January — 



At one metre below the surface, 21° 2' Centigrade. 



„ two metres, „ 21° 5' „ 



At Paindra, more than 1,000 feet lower than Umerkuntuk, the 

 temperature was, 27th to 29th of January — 



At one metre below the surface, 20° 0' Centigrade. 



„ two metres, „ 21° 0' „ 



I observed similar differences at Ramgurh, and at some other 

 stations West and Nortli of Umerkuntuk, which are all 1,000 to 

 1,300 feet lower than the plateau. 



