330 LA TOUCHE : GEOLOGY OF NORTHERN SHAN STATES. 



(c) River Alluvium. 



The broad straths along the river and stream courses, which 

 r,. „ . constitute the only permanently cultivated 



Kiver alluvium. ■* J 



ground in the States, are generally composed 

 of clays, more or less sandy according to the nature of the rock 

 drained, of grey or yellow colours contrasting strongly with the 

 red clay of the surrounding hill slopes. They contain a consider- 

 able proportion of calcareous matter, deposited from solution, and 

 are extremely fertile when irrigated, as is almost invariably the 

 case ; the ground being artificially terraced up to the highest point 

 at which water from the hills can be led on to the fields, often 

 through wt?ll engineered channels of considerable length. The prin- 

 cipal crop grown on these irrigated fields, known as ' Na ' culti- 

 vation, is paddy or rice, but a certain proportion of leguminous 

 crops is also produced. Tobacco is mainly grown along the banks 

 of the rivers, on the beds of rich silt left when the floods have 

 subsided ; and among the Eastern Ranges, oranges are largely 

 grown along the smaller streams, on the narrow triangular area 

 of rich alluvial soil which is found where the ravines open out 

 into the main valley. 



(d) Peaty Deposits. 



In certain localities, usually on the gentlu slopes surmounting 

 , . the crest of a scarp, the water issuing from 



Peaty deposits. , . ■*• .. . ~ 



springs, instead of depositing its burden of 

 calcareous matter at once, sweeps away the covering of red clay, 

 or perhaps prevents its formation. In such places a rank growth 

 of aquatic plants and grasses springs up, and in time gives 

 rise to the accumulation of a black soil resembling peat, among 

 which outcrops of the solid rock may generally be found. These 

 peaty areas are often of considerable dimensions, and may be easily 

 recognised by the short green grass which covers them and by the 

 absence of trees. They are common about Nawnghkio, the station 

 on the southern side of the Gokteik gorge, and they seem to be 

 almost confined to such positions as this, that is to say, where the 

 plateau is gently undulating and there is no very high ground in 

 the neighbourhood, so that the water of the springs has no very 

 long course underground, and is consequently not saturated with 

 carbonate of lime. 



