320 LA TOUCHE : GEOLOGY OF NORTHERN SHAX STATES. 



This seems to show that at one time the floor of the valley was 

 occupied by a lake, since the present insignificant stream carries no 

 fish that could be caught with hooks of the size found, and the 

 manner in which these and the stone implements occur suggests 

 their having been dropped from boats, which there is now not 

 water enough to float. The narrow and precipitous gorge through 

 which the stream now escapes from the valley also suggests that 

 at one time a lake lay above the exit ; and it is probable that the 

 rock}' floor underlying the ruby gravels lies below the lip of the 

 falls, and therefore forms a true rock-basin. 



Another old terrace deposit in the same neighbourhood has been 

 Rub ravel Namhsu described by Dr. Noetling. 1 This is situated 

 hka." Jgrave " amisu j n valley of the Nam-pai, about 15 miles 



to the west of Mong Long (Mainglon) and 

 at the junction of a small stream, the Namhsu-hka (Namseka), 

 with the main river (C 1). The ruby-bearing gravel here seems 

 to be the remains of an old terrace deposited by the Mogok river, 

 which joins the Nam-pai at this point, at a time when the valley 

 had not been cut down to its present level ; for the rubies con- 

 tained in it must have been brought down from the Mogok valley, 

 the only direction in which the crystalline limestone, which con- 

 stitutes the matrix of the gems, has been found. 



The tourmaline gravels of Mong Long were also described by 



Dr. Noetling in the same part of the Records. 2 



M?ng U SnI ine8raVelS ° f The F are situate d hi g her U P in the valle y of 

 the same river, the Nam-pai, and are found 



along both sides of it, extending for about five miles eastwards 

 from a point about two miles north of the town of Mong Long. 

 The boulder and gravel deposits forming the terraces reach, ac- 

 cording to Dr. Noetling, to a height of about 200 feet above the 

 river, and consist mainly of quartz pebbles and boulders ; evi- 

 dently an old fan-talus derived from the hills to the north, which 

 are composed of gneisses with bands of tourmaline granite, trav- 

 ersed by numerous quartz veins. The pebbles of blue shale or schist, 

 also mentioned by Dr. Noetling, probably come from the hills to 

 the south. It does not seem possible that such coarse deposits 

 as these could have been accumulated on the bed of a lake, as 

 he suggests, and the red clay which he speaks of as overlying the 



> The Namseka Ruby Mine ; Records, Oe.ol. Surv. Ind., Vol. XXIV, Pt. 2, p. 1.19. 

 2 The Tourmaline Minos in the Mainglon State; Ibid, p. 125. 



