306 LIEUT.-COLONEL S. G. BURRARD ON THE 



that these large deflections of gravity are not confined to exceptional localities, but 

 prevail throughout a vast region. 



In October, 1903, Captain COWIE was directed to extend the Great Arc of India 

 northwards across the Mussooree hills to the snowy range, and to observe for latitude 

 in the inner Himalayas. High authorities had expressed the opinion that the large 

 deflections of gravity at Dehra Diin, Birond, and Phallut were due not to the 

 Himalayan mass, but to the peculiar geological formation of its lower and outer 

 range ; that these deflections would be found to disappear when the first Himalayan 

 ridges were crossed, and that large southerly deflections would be met with in the 

 inner Himalayas. Captain COWIE extended the Great Arc of India into the 

 mountains from latitude 30 29' to 31 1', a distance of 35 miles, and he observed for 

 latitude at the Himalayan stations of Bahak (9715 feet high), Bajamara (9681 feet), 

 Lambatach (10,474 feet), and Kidarkanta (12,509 feet). Table IIlA. shows that 

 large northerly deflections were met with at all these stations. 



The form of the ideal section deduced in fig. 3, Plate 14, from pendulum results 

 rather justified the belief that deflections would be found to decrease rapidly between 

 Station 41 (Mussooree) and Station 43 (More). The northerly deflection of 30" now 

 discovered by COWIE at Kidarkanta* consequently throws doubt on the correctness 

 of that portion of the pendulum section that lies between these two stations, and 

 confirms the opinion that a greater excess of matter exists at More" than has been 

 deduced from BASEVI'S observations. 



In Plate 17 is given a cross-section of the Himalayas, drawn by Captain COWIE, 

 through the stations of Kidarkanta and More" ; this section is not ideal but real ; it 

 shows the variations in the actual level of the ground, and illustrates the visible 

 mountain mass separating the two stations ; the vertical scale is twenty times as 

 great as the horizontal. 



Plates 18. 19 and 20, drawn by Captain COWIE, give cross-sections of the Himalayas 

 at Kidarkanta, Birond, and Phallut ; they illustrate the increase in elevation between 

 the plains of India and the plateau of Tibet at three different places. In each the 

 vertical scale is ten times as great as the horizontal ; the scales employed in these 

 three last plates are larger than those used in Plate 17. 



* As an observer penetrates a mountain range, he leaves more and more of the mountainous mass 

 behind him ; the attraction of the portion left behind is then opposed to the attraction of the masses still 

 confronting him, and tends to decrease the resultant deflection of his plumb-line. To determine the 

 relative effects of the rearward and forward masses a contoured map is necessary. 



