1888.] Myelat District of the Southern Shan States. 385 



Scotland and elsewhere, and which are due to percolating water dissolv- 

 ing the limestone and forming superficial holes into which the overlying 

 peat or soil gradually sinks.* The same general principle governs of 

 course both cases ; but in Scotland there is only a thin covering of 

 peaty soil overlying the limestone, whereas in the Shan hills we have a 

 considerable thickness of fine red clay. It thus happens that in the first 

 case we get only a few shallow holes, whereas in the latter vast masses 

 of clay have been in the course of ages carried into the bowels of 

 the earth, resulting in the excavation of extensive depressions, the entire 

 drainage of which is carried away by subterranean channels. 



The progress of the excavation of these depressions can be seen 

 in every stage. The conditions of the phenomena, it must be remem- 

 bered, are a thick covering of fine clay resting on a flooring of weather- 

 worn limestone. The limestone abounds in holes and cracks, into one 

 of which, at any given spot, the rain-water, percolating from above 

 through the red clay, finds its way. This carries with it some of the 

 clay from just above the hole, and a commencement has been made. 

 Next rainy season more water finds its way by the same route and more 

 of the sub- soil is subtracted. In a few months or years, the overlying 

 clay becomes largely undermined and sinks down, and we get either a 

 small crater, if the stratum of clay be not more than a few feet thick, 

 or, if the clay be thicker, a broad circular depression in which rain- 

 water will collect to carry on the process. Now, a similar process will 

 be simultaneously going on at other points more or less adjacent to that 

 we have been considering, and, in the course of time, the several craters 

 or depressions thus formed will meet and coalesce. The water as it 

 escapes through the underlying rock will enlarge its channels of exit by 

 dissolving the limestone : more of the overlying red clay will year by 

 year be removed : the area drained and the volume of water escaping 

 will gradually augment : the ridges separating the contiguous centres 

 of action will gradually disappear, and it is not difficult to understand 

 how in the course of ages, that is, since the surface of the red clay became 

 upraised into dry land, we shall in this manner at last find large areas 

 of depression draining into underground channels. 



These areas may even at the present time be seen in every stage 

 of formation. There is the small crater-like opening 30 or 40 feet 

 across which opened out last year, perhaps in the middle of some poor 

 man's field, with its broken precipitous sides and ragged edges : there 

 is the wide gently sloping valley extending over several hundred acres, 



* See Prof. A. Geikie, " The Scenery of Scotland viewed in connection with its 

 Physical Geology," 2nd edition, p. 36. 

 50 



