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



Upper Burma in 1887, and, under the auspices of the Governor- 

 General of India the Marquis of Ava and with the assistance of 

 the military and civil authorities of Burma, was enabled to make a 

 geological survey of the district and prepare a report for the use of 

 the Home Government. The large series of specimens collected to 

 illustrate this report was entrusted to the other author for descrip- 

 tion, and he has prepared the portions of this memoir dealing with 

 the petrology and mineralogy of the district. 



It was in a memoir read before this Society in 1798 that the crys- 

 tallised oxide of aluminium was shown by Greville to be a definite 

 mineral species, to which he gave the name of ".corundum ;" while, 

 in an appendix to this mfmoir, the Count de Bournon exactly deter- 

 mined the crystalline form of the mineral. Four years later, the last- 

 mentioned author submitted a second paper to this Society, in which 

 the mode of occurrence of the mineral in Ceylon and in the Salem 

 District in Southern India was fully discussed. Twenty years later, 

 Leschenault de la Tour, while on a scientific mission to Southern 

 India, collected and sent to Paris a remarkable series of rocks from 

 the gem-bearing districts. Quite recently, an able French mineralo- 

 gist and petrographer, M. A. Lacroix, has described the series of 

 specimens in the collections made by de Bournon and Leschenault de 

 la Tour. Much light has been thrown on the mode of occurrence of 

 the corundum in India by the labours of Mr. F. M. Mallet, Dr. V. 

 Ball, and other members of the Geological Survey of that country ; 

 the remarkable emery deposits of Asia Minor have been thoroughly 

 studied by the late J. Lawrence Smith and Professor G. Tschermak ; 

 while the occurrence of corundum in the Eastern States of North 

 America has formed the subject of important memoirs by Dr. Genth 

 and other authors. 



The famous ruby district of Upper Burma was almost unknown to 

 Europeans before the annexation of the country by the British. It 

 is situated about 90 miles N.N.E. of Mandalay, and about 11 miles 

 E. of the military post of Thebayetkin, on the Irrawaddy. The 

 tract, so far as explored, is about 26 miles long and 12 broad, and 

 lies at elevations varying from 4,000 to 5,500 feet above the sea-level. 

 The principal mining centre in this district is Mogok, and the present 

 workings for rubies extend over an area of 45 square miles ; old 

 workings, however, being found over an area of 66 square miles. The 

 principal mining operations are carried on in the three valleys of 

 Mogok, Kathay, and Kyatpyen ; but there are some smaller outlying 

 districts, in which mines were formerly worked, in the Injouk Valley, 

 near Bernardmyo, at Wapudoung, 11 miles E. of Thebayetkin, and at 

 Launzee, 8 miles S.W. of Kyatpyen. There is also a small tract of 

 rnby-bearing rocks (crystalline limestones) at Sagyin, 24 miles N. of 

 Mandalay ; and it is asserted by the natives that two other lime-' 



