70 



R. S. Brough — Maynetic Elements for Northern India. [Feb. 



The dip appears to have been measured for the first time when the 

 French Corvette " La CJievrette'" visited these waters in 1827, by M. de 

 Blosseville who found it to then be* 



26° 32' 38" 

 Ten years later, in 1837, on the occasion of the visit of another French 

 Corvette " La Bonite"" to the Hugli river, the dip was measured at Kala- 

 gachia (Diamond Harbour) by the chief Hydrographer, who found it to bef 



26° 89' 04^" 

 exhibiting a change of only 0° 06' 26 from the result of the earlier 

 measurement. 



The next and most recent measurement, was made by the brothers 

 Schlagintweit in March 1856 and in April 1857, in which years it Avas 

 found to be respectively :J: 



28° 06' 43" 

 and 28° 22' 56" 

 The same observers found the dip at Jabalpur in December 1855 to be§ 



28° 3r 08" 

 Their measurements of the horizontal force gave : — 



0'373S6 dynes at Calcutta in March 1856 

 0-36644 „ „ in April 1857 



0*39959 „ Jabalpur in December 1855 



A very valuable series of observations was made in 1867-68 by the late 

 Captain Basevi, R. E., under the orders of Colonel J. T. Walker, C. B., R. E., 

 Superintendent of the G. T. Survey (now Surveyor- G-eneral of India,) 

 at 14 stations extending from 15° 6' to 30° 20' North latitude, || but none 

 of them are coincident with the three stations under consideration. 



The values of the dip and horizontal intensity at the limiting stations 

 of the series were as follow : — 



Stations. 



Latitude. 



Longitude. 



Date. 



Horizontal 

 intensity. 



Dip. 



Namthabad, . . 

 Peyrah, ...... 



15*' 06' 00" 

 30° 20' 00'' 



77° 36' 00" 

 78° 06' 00" 



April 1868 

 Jan. 1867 



0-37401 

 0-33604 



11° 40' 56" 

 41° 27' 34" 



* " Asiatic Researches" Vol. XYIII, Part I, p. 4. 

 t Proceedings, Asiatic Society of Bengal, Wednesday, 3rd May, 1837. 

 % Observations in India and High Asia, Yol. I. 

 § Loc. at. 



II General Report of the Operations of the Great Trigonometrical Sm-vey of India 

 during 1867-68. 



