390 Mr. C. B. Brown and Prof. J. W. Judd. [Mar. 7, 



Mining operations for the obtaining 1 of rubies are carried on in 

 Burma in four different ways. (1.) In the alluvia, "twinlones," 

 square pits from 2 to 9 ft. across, ingeniously timbered with bamboo, 

 are sank to the ruby earth, the drainage of the pits and the removal 

 of material being effected by baskets attached to balance poles, both 

 made of bamboo. (2.) In the hill-wash long open trenches, called 

 " hmyaudwins," are carried from the sides of a gully, and the earth 

 is washed out by streams conveyed into the trenches by bamboo 

 pipes. (3.) In the caves and fissures filled with earth which abound 

 in the limestone rocks, regular mines " loodwins " are opened, and 

 the productive ruby earth is followed for long distances by means of 

 shafts and galleries. (4.) The limestones which contain the rubies 

 are at one or two points quarried, and the gems are obtained by 

 breaking up tLe rock masses. 



The extensive rubellite mines at Nyoungouk are worked in a 

 somewhat similar plan to the " hmyaudwins." Water is delivered 

 by a number of bamboo pipes at the head of the almost vertically 

 exposed faces of alluvium ; and as the masses of the latter are 

 loosened, the miners dash water upon them from shovel-shaped 

 baskets, and are able to detect and pick out by hand the brilliantly 

 coloured stones exposed on the washed surfaces. 



The petrology of this district of Upper Burma, in which the rubies, 

 spinels, and rubellite occur, presents features of the greatest geolo- 

 gical interest. In many respects the petrology of Burma exhibits close 

 analogies with that of the corundiferous localities of Ceylon, the Salem 

 District, and other portions of the Indian peninsula ; but some of the 

 phenomena presented by the rocks of the Burma ruby district do 

 not appear to find a parallel in any of the gem-yielding tracts 

 described by de Bournon and more recently by Lacroix. 



The general mass of gneissic rocks composing the mountainous 

 district in which the ruby localities are situated are of intermediate 

 chemical composition, and consist of biotite-gneisses, biotite-granu- 

 lites, and, more rarely, biotite schists rocks in which hornblende is 

 rare or altogether absent, but which, on the other hand, are often 

 remarkably riah in garnets. Neither corundum nor spinel have been 

 certainly detected in these rocks. 



Interfoliated with these ordinary gneissic rocks, which form the 

 great mass of the mountains, we find rocks of much more acid com- 

 position, including very coarse pegmatites and graphic granites, 

 aplites and granulites (leptynite or Weiss-stein), granular quartzites, 

 and orthoclase-epidote rocks. The orthoclase of these rocks fre- 

 quently contains inclusions of fibrolite and other minerals, it often 

 exhibits the " murchisonite '* modification and partings, and is not 

 unfrequently converted into " moonstone ;" still more complete altera- 

 tions of the orthoclase into epidote, muscovite, and kaolin being by 



