DEVONIAN SYSTEM • PLATEAU LIMESTONE. 



183 



deposits of calcareous silt, and where water is easily obtainable by 

 a system of irrigation channels, that continuous cultivation can be 

 carried on. Elsewhere, on the hill slopes, it is quickly impoverished, 

 and the clearings will only produce crops for an average period of 

 four years, after which they are allowed to lie fallow until the 

 scrub has grown up again, when it is cut down and burnt, and the 

 process is repeated. The water that falls on the slopes too is 

 either run off at once by the stiff impervious clay, or sink3 deep 

 below the surface th ough fissures in the limestone. No systematic 

 attempt is made to terrace these steeper hill slopes, though some- 

 times the soil is allowed to collect against a fallen log or a rock ; 

 but if this were done it would certainly reta-d the impoverishment 

 of the soil for a much longer time. The addition of lime to the 

 clay, which could easily be done by the cultivators if they were 

 possessed of suffici nt energy,— for limestone may be obtained every- 

 where, — would doubtless tend to its amelioration ; for it is a curious 

 fact that, though the rid clay has been derived, to a great extent, 

 if not entirely, from the dir. integration of the limestone, analyses 

 show that it contains no irace of lime. Among wild plants the common 

 bracken fe;n, Pteris a^uilina, is found universally over the lime- 

 stone a x a, and is often of use in detei mining the limits of the 

 fo:mation whi n no ou c ops are visible, 1 hough it is by no means 

 confined to this area. 



Thj Plateau Limes. one is known to extend far to the south 

 . into the Southern Shan States and the Karen 



country, and is probably continuous with the 

 limestones in which the well known guano caves of Moulmein are 

 situated. To the south of Moulmein it continues through Tenas- 

 serim, but has hilheito been described only f.om isolated locali- 

 „ ., . ties, since no connected survey of that country 



Fossils in lenasserim. , , , , . „ , - , 



has yet been made. A small number of tos- 



sils was collected from these rocks in Tenasserim several years ago 

 by Mr. P. N. Bose, and were described by Dr. Noetling, 1 who 

 pronounced them to b- of Carboniferous (p obably upper Carboni- 

 ferous) age. 2 



1 Carboniferous Fossils from Tonasserim ; Records, Oed. 8wv. Ind., Vol. XXVI, 

 Pt. 3, p. 96. 



2 Previous to this fossils had been found in Tena-sacrim by Dr. Oldham (.SW. Htcordi, 

 Govt, of India, No. X, p. 33), and by Mr. Theobald in the limest men near Moulmein 

 (Geology of Pegu; Menu/Ore, Qcol. Surv. Ind., Vol. X. Pfc. 2, p 1381 .Both of these 

 observers considered the fossils to be of Carbar if xous ages but they were never described 

 and are now lost. 



