278 Notes on the Geology, $c. of Maulamyeng. [May, 



rapidity of the current, but spreading themselves across, obstruct its 

 passage, and render the navigation extremely dangerous at any other 

 time than the N. E. moonsoon. The current of the river is very 

 strong near Miang and Mye-an, but the principal rapids are met with 

 in the neighbourhood of Towng-bio-myo : I accompanied Sir J. Dick- 

 son, K. C. B., to this place in March, 1835, and we found it impossible 

 for our boats to proceed further ; indeed our return was not effected 

 without considerable risk, owing to the force of the current, and the 

 numerous eddies produced by the inequalities on the bed of the Than- 

 Iweng, which is in this place extremely deep. Accidents continually 

 occur : a boat once drawn within the vortex of the whirlpool is inevi- 

 tably lost ; both boat and crew are sucked down, and never known to 

 make their appearance on the surface. 



At the mouth of the Yengbieng Kyowng, a spot rendered peculiaidy 

 attractive by the beauty of the surrounding scenery, the limestone is 

 seen gradually passing into clay-slate ; the limestone has a slaty frac- 

 ture, becomes earthy, and is of a darker colour ; the transition is at 

 length so perfected (to the view) that but for the effervescence produced 

 by the nitric acid, it becomes, in some instances, extremely difficult to 

 detect the presence of the limestone in the argillaceous schist, with 

 which it is intimately blended. At a short distance beyond the Yeng~ 

 Men Kyowng, a few blocks of a grey siliceous rock may be observed 

 at the foot of a hill on the left bank of the Than-lweng* ; the hill is 

 high, of a conical shape, and covered with a thick forest and under- 

 wood. Iron ore is found in considerable quantities both on the hill, 

 as well as in its vicinity ; and small grains of iron pyrites are abun- 

 dantly disseminated in the rock. This is succeeded again by the 

 slaty limestone, and finally by the blue clay-slate that crosses the river 

 at the Towng-bio rapid. Large masses of slate repose on either bank, 

 surrounded by a micaceous sand and pebbles (consisting for the most 

 part of talcose slate), brought down from the upper country during the 

 S. W. moonsoon. A dyke of porphyrinic felspar intervenes between 

 the slate strata ; the felspar rock is of a deep yellow, and studded 

 throughout with small circular pieces of the same mineral, of a lighter 

 colour. I regret much that I had not leisure to pay a proper degree 

 of attention to the structure of this rock ; our party arrived on the 

 ground late in the afternoon, and we left the place early on the fol- 

 lowing morning ; but short as was my stay at the Towng-bio rapid, I 

 have often since dwelled in pleasing recollection, on the wild and 



* The rock is extremely hard, and slightly impregnated with carbonaceous 

 matter. 



