623 



hills, and the error by trigonometrical levelling is 16-50 feet, or 

 0-008 foot per mile. 



" When the great Indus series is finished, the sea-level will be 

 brought up to the Chueh base line, and from thence along the north- 

 west Himalayan series to Dehra Dun. The result of this series will 

 give another verification, which will be especially valuable, as it is 

 intended to level along the flat valley of the Indus by special level- 

 ling operations. It is also proposed to carry special levelling ope- 

 rations from Dehra Dun to Calcutta. Pending the completion of 

 these undertakings, it has been found necessary to correct provi- 

 sionally the results given by trigonometrical levelling, in order to 

 disperse the discrepancies above shown, and reduce the results of the 

 three data for sea-level near Calcutta, Bombay, and Karachi. The 

 results, so reduced, become comparative, inter se, and are required 

 for record on the general maps." 



The upshot of all this is, that Colonel Waugh has provisionally 

 applied the following corrections to the two sections of the great arc, 

 as given in synopsis A, p. 248, and synopsis B, p. 53, of my book 

 of 1847, in lieu of those formerly applied; and I must say that I 

 think they will be nearer the truth than those given in that book, 

 because the discrepancy specified in the note at the foot of p. clxxi., 

 taken into combination with all the results of the general trigono- 

 metrical survey since obtained, certainly point to some error in 

 Colonel Lambton's operations to the south of Damargida. The 

 two sections, applying Colonel Waugh' s corrections, will stand as 

 follows : 



SECTION A. 



Feet. 

 Length of the arc deduced from the Sironj base .... 1961 155'422 



Add correction for 1 11-14 feet in height at ditto 10-412 



Add correction q, as explained in p. clxxi 12-387 



Total arc, Kalianpur to Kaliana, by provisional data 1961178*221 



SECTION B. 



Feet. 

 Length of the arc deduced from the Sironj base 2202914-322 



Add correction for 111-14 feet in height at ditto .... 1 1-695 



Add correction rj, as explained in p. clxxi 8*679 



Total arc, Kalianpur to Damargida, by provisional data 2202934-696 



