Royal Society. 233 



outline of the continent of Asia. On this was laid down a polygonal 

 figure DEFGHIJKL, (which for convenience the author calls the 

 " enclosed space,") marking the boundary of an irregular mass, 

 which is the only part of the earth's surface that appears to have a 

 sensible effect on the plumb-line in India. The boundary of this 

 space is thus defined : — 



DEF is the Himalaya range, having a bend at E from north-west 

 on the left, to east-by-south on the right. FG is a range running to 

 the table-land of Yu-nan in lat. 25° and long. 103°. GH is the 

 range of the Yun-Ling mountains, in which there are many peaks of 

 perpetual snow. HI is the Inshan range. IJ is the Khing-khan 

 range, very steep on the east side, not so on the west ; the passes 

 are said to be 5525 feet above the sea. JK is the Altai range, the 

 highest peak of which is 10,800 feet; the average height is 6000 : the 

 range declines towards the east. KL was once thought to be a 

 range of mountains, but is now found to be a line of broken country. 

 LD is the Bolor range, rising to an elevation similar to that of the 

 Hindoo Koosh. There are besides these two ranges of mountains 

 running into the enclosed space, parallel to the Altai and Southern 

 Himalayas, namely the Thian-Schan range, or Celestial Mountains, 

 and the Kuen-Luen range, being a continuation of the Hindoo Koosh, 

 which rises from an altitude of 2558 feet near Herat to about 20,000 

 where it meets the Bolor range. It is, however, with the elevation 

 of the enclosed space itself that we are principally concerned, since 

 ranges of mountains have not so important an influence, when 

 distant, as table-lands of elevation. 



Before describing the country within these limits, the author gives 

 a general sketch of the parts which lie outside, from which it ap- 

 pears that the calculations may be confined to the enclosed space. 

 He then describes in detail the nature of the country within the 

 boundaries of the enclosed space, commencing with the Himalayas, 

 which rise abruptly from the plains of India to 4000 feet and more, 

 and cover an extensive broken space some 100 or 200 miles wide, 

 rising to great heights ; perhaps 200 summits exceed 18,000 feet; 

 the highest reaches to more than 28,000. The general base on 

 which these peaks rest rises gradually to 9000 or 10,000 feet, where 

 it abuts on the great plateau north of the range. The character of 

 the country to the south of this plateau is much better known than 

 that to the north. If a circle with a radius 5 o, 046 (the value of one 

 of the pdii employed in the dissection) be drawn around Kaliana, 

 it will pass over the highest part of this plateau. This circle divides 

 the enclosed space into two portions, of which the southern is called 

 by the author the "Known" and the northern the "Doubtful 

 Region." The effects of the two portions are separated in the cal- 

 culation by the introduction of an arbitrary factor. 



After describing the doubtful region, as far as was possible from 

 the data to which he had access, the author assumes, as the best 

 general representation of the facts, that to the north of a line run- 

 ning through Leh and H'Lassa the doubtful region slopes gradually 

 from 10,000 feet down to 2500 along a parallel line nearly in its 

 centre, and then rises again at the same angle to the north, and that 



