1857.] Report on the Progress of the Magnetic Survey. 101 



and from Madras via Trichinopoly to the Neilgherries and back, 

 have been determined by repeated barometric and hypsometric 

 observations. 



Particular attention was paid throughout this season to the tem- 

 perature of the ground at various depths below the surface. 



We have been fortunate enough to obtain very regular and 

 careful observations of the temperature of the ground from the 

 surface down to a depth of two metres (6| feet) for the last twelve 

 months from Madras and Calcutta. They were made at Madras 

 under the superintendence of Major "Worcester and of Major Jacob, 

 and at Calcutta under the superintendence of Major Thuillier : 

 the instruments used were brought out by us, were similar to those 

 used by ourselves, and had been all carefully compared. 



This will enable us to correct our own observations, made at 

 various stations for the changes of temperature taking place from 

 one month to another, and to make them all strictly comparable by 

 reference to one common standard. 



Our observations show that great confidence may be placed in 

 the temperature of the ground, ascertained thus directly by ther- 

 mometers buried at different depths below the surface, and the 

 results for the decrease of the temperature, with height calculated 

 from different stations, agree remarkably well. It seems that the 

 temperature of springs is more liable to be effected by local causes 

 connected with their mode of origin, &c. than the temperature of 

 the dry ground, thus ascertained directly. 



The following Table shows the temperature of the ground at 

 some of my stations, where observations have been conducted for 

 some time, in various localities : — 



Temperature of tlie Ground at 2 metres (6^ feet) below the surface 

 at some Stations letiveen Agra and the Neilgherries. 



Temperature, 

 centigrade. 



Agra, 23rd February to 4th March, 1856, 23° 5' 



Jubbulpore, 22nd to 27th December, 1855, 22 8 



Sitabuldee, near Nagpore, 3rd to 9th January, 1856, 28 6 



The temperature of the ground in the plains about Nag^ 



