PHYSICAL GEOLOGY. 



25 



what must have been a widespread formation. In the Southern 

 States they have not been denuded away to the same extent, and in 

 that part of the country caverns are said to be of common occur- 

 rence, though I am not aware that any of them have been exjjlored. 1 

 Several large caverns occur in the same limestone far to the south, 

 near Moulmein in the Amherst District of Lower Burma, and have 

 been described by more than one writer. 2 



The cave of Shwe Male, near the foot of the hills about 8 miles 



east of the Irrawaddy at Singu, above Man- 

 Cavern at Shwe Male. , , . .. , . met? 1 o- TT * 17- 1 



dalay, was visited in looo by bir Henry Yule 

 and Dr. T. Oldham, who have given a very full description of 

 it. 3 This cavern, however, is not in the Plateau limestone but in 

 the crystalline limestone associated with the Archaean rocks of the 

 Ruby Mines District. 



The larger depressions or ' caldron-valleys ' (Kesseltaler) are 

 , , , found along the flanks of the ranges to the 



Origin of caldron-valleys. ,#,11, i ,,1- , 



east 01 the plateau, where the limestone has 

 been thrown into folds together with the underlying rocks, and 

 has then been denuded from the crests of the anticlinals, so that 

 we have on either side a more or less precipitous scarp of limestone 

 facing the central ridge of the range. The streams flowing 

 down ravines in the latter strike against this wall of limestone, and 

 find their way through it underground, issuing in the deeper valleys 

 beyond. In this way enclosed valleys are excavated, varying 

 in size from mere ravines a few hundred yards across, to a valley 

 like that in which the village of Lukhkai (II), on the south side 

 of the range east of Lashio, is situated (Plate 3). This valley is 

 about 4 miles in length by 2| in breadth, and contains more than 

 one subsidiary depression or ' swallow- hole ' within its area (Plate 4). 

 In these valleys the stream that flows through them generally disappears 

 abruptly beneath a vertical wall of limestone into the mouth of a 

 small cave, but in other cases there is no visible outlet, the water 

 soaking through the soil that fills the bottom of the hollow, which 

 becomes a morass during the rainy season. 



1 See Middlemiss, in Gen. Report, Oeol. Surv. Ind., 1899-1900, pp. 131, 138. 



2 \V. l'oley, Notes on the Geology, etc, of the Country in the Neighbourhood of 

 Maulamyeng (vulg. Moulmein), Journ. As. Soc. Beng., Vol. V, p. 273, 1836. 



S. It. Tickell, itinerary through t he southerly portions of the district of Amherst, 

 Province of Tenasserim, ibid, Vol. XXVIII, p. 425, 1859. 



8 A Narrative of the Mission to the Court of Ava in 1855, pp. 177, 330. London, 1858. 



