42 
Records of the Geological Survey of India. 
[vol. IV. 
distinction between them is merely one of degree) that is, in detached outbursts assuming 
the proportions of low hills, and as veins or dykes traversing the ‘ axial’ strata. The most 
important development of this rock, throughout the country north of the parallel of 
Akouktoung, is the Bidoung hill, five miles south by east of Pathi. This serpentine area is 
five miles in length by from two to two and a half in breadth and is divided by the Mahton : 
Bidoung standing on ike west side, faced on the east by a hill of hardly less height. 
These two hills indicate the great bulk of the seipentine along an axis stretching north 
by east, but from the easterly hill a small range runs nearly due south impinging on the 
Mahton at Keinggye, though the serpentine stops just short and is not seen here in the river. 
This most important development of serpentine illustrates the remark I have before made 
of that rock affecting the outer rather than the central hills. Descending the Mahton from 
tht north, Bidoung bill is seen straight ahead of the river channel, and so distinctly is the 
bulk of Bidoung dissociated from the spurs of the main range, that without reference to 
the map. it is doubtful which side of the hill the Mahton is about to flow, hilt, on reaching 
the hill it flows round its east flank through one of the prettiest gorges conceivable. The 
character of the rock is proclaimed by the stunted vegetation covering it, but where 
cracks have allowed the retention of moisture, trees, especially the Tliitsi (Mdanorrluea 
nsitatissimn), have taken hold, favored of course by the generally cooler and moister air of 
the country close to the densely wooded main range. Larg'e surfaces of rock, however, are ab¬ 
solutely and in the most literal sense bare of all verdure and impart a distinctive character 
which, once seen, cannot be mistaken. I have already remarked on the metamorphism de¬ 
veloped among the ‘axials’ on the flanks of Bidoung, but the intrusion of this mass of 
seipentine seems to have produced oven a greater mechanical result, in the deflection of the 
axial boundary here to the eastward. The boundary is not perhaps so sharply defined as 
in some spots, but I regard the channel of the Moo sti-eam as very neai'ly coinciding with 
it, or in fact resulting from it. South of Lepangain, too, the boundary seems to find 
physical expression in the conformation of the surface, hut for a few miles east of Lepan¬ 
gain the boundary is obscure, and few rocks are seen through the jungly undulating country 
which intervenes. The fact of the general outward deflection of the boundary is not, 
however, in the main aifeeted by a little ambiguity in detail, and the curve so corresponds 
to the great mass of Bidoung serpentine, that taken together with the excessively disturbed 
condition of the rocks hereabouts, we are forced to regard the cause of these appearances 
as nothing more nor less than the mechanical intrusion of that hill mass. 
The next considerable development of serpentine occurs as a low narrow ridge of 
some three miles in length intersected by the Made stream, and situated on the j unction of 
the axial and nummulitie groups. This ridge, which must often he less than the third of a 
mile in breadth, seems as though it were a huge dyke or wall of rock occupying at this 
spot the boundary itself. Above it very considerable disturbance exists among the axials, and 
enormous masses of the limestone are seen in the bed of the stream, much aifeeted both 
chemically and mechanically. This action is not so well, if at alt, noticed in the nummulitie 
group, and whereas the upper axials are repeatedly seen thus altered, 1 do not remember any 
similar amount of metamorphism in the nummulitie group, though here it is contiguous to a 
very considerable mass of serpentine which has characteristically affected the lower group. 
The next considerable mass of serpentine is that which constitutes Nattoung a pro¬ 
minent hill between the Made and Tkanni streams. The rock here rises into two peaks, 
that of Skiubaian to the north-west and the somewhat higher one of Nattoung to the south¬ 
east, giving a length of about three and a half miles in its long axis. 
Two miles west of Laidi on the Thanni channel occur two small patches of serpentine 
forming the twin peaks of Tkitsidoung and Hnordoung. These patches are separated by 
