460 REPORT OF NATIONAL MUSEUM, 1899. 



this gum as a product of trees of the same species as those at present 

 producing the raw gum called by the natives and Arabs sandarusiza 

 miti or chakazi ; that is, the Trachylobium mozambicense Peters. The 

 gum when dug from the soil has superficially a peculiar pebbled ap- 

 pearance, best described as "goose skin " (Specimens Nos. 62472, 62473, 

 U.S.N.M.), and which Burton considered as due to the impress of the 

 sandy grains in which it had been buried, but which Dr. Kirk regards 

 as due to the structure of the cellular tissues of the tree. The copal 

 when dug up has, according to this authority, exteriorly no trace of 

 the loose skin structure. 



As is the case with the New Zealand and West African gums, the 

 methods of digging are very crude, careless, and desultory. The 

 diggings are mostly beyond the jurisdiction of Zanzibar, but as this is 

 the principal port, most of the material is known commercially as 

 Zanzibar copal. 



BIBLIOGRAPHY. 



M. C. COOK. Report on Gums, Resins, Oleo-Resins, and Resinous Products in the 

 India Museum, or produced in India. 



London, India Museum, 1874, pp. 98-103. 



S. F. PECKHAM. Report on the Production, Technology, and Uses of Petroleum and 

 its Products. 



Report of the Tenth Census of the United States, X, 1880. 

 This important report contains a very complete bibliography on the subject up 

 to date of publication. 

 G. W. GRIFFIN The Kauri Gum of New Zealand. 



U. S. Consular Reports, II, 1881, p. 241. 

 R. W. RAYMOND. The Natural Coke of Chesterfield County, Virginia. 



Transactions of the American Institute of Mining Engineers, XI, 1882, p. 446. 

 EDWARD ORTON. A Source of the Bituminous Matter in the Devonian and Sub-Car- 

 boniferous Black Shales of Ohio. 



American Journal of Science, XXIV, 1882, p. 171. 



ORAZIO SILVESTI. On the Occurrence of Crystallized Paraffin in the Hollow Spaces 

 of a Basaltic Lava from Paterno, near Mount Etna. 



Journal of the Society of Chemical Industry, I, 1882, p. 180. 

 WILLIAM MORRISON. The Mineral Albertite and the Strathpeffer Shales. 



Transactions of the Edinburgh Geological Society, V, 1883-1888, p. 34. 

 -. A New Mineral Tar in Old Red Sandstone: Ross-shire. 

 Transactions of the Edinburgh Geological Society, V, 1883-1888, p. 500. 

 S. F. PECKHAM. The Origin of Bitumens. 



American Journal of Science, XXVIII, 1884, p. 105. 



EDWARD ORTON. The Trenton Limestone as a Source of Petroleum and Natural 

 Gas in Ohio and Indiana. 



Eighth Annual Report U. S. Geological Survey, Pt. 2, 1886-87, pp. 483-662. 

 J. L. KLEINSCHMIDT Asphalt Deposits in the Formation of Coal. 

 Berg- und Huttenmannische Zeitung, XLVI, 1887, p. 78. 



JOSEPH M. LOCKE. Gilsonite or Uintahite. A New Variety of Asphaltum from 

 the Uintah Mountains, Utah. 



Transactions of the American Institute of Mining Engineers, XVI, 1887, p. 162. 

 A. RATEAU. Note sur 1' Ozokerite, ses Gisements, son Exploitation a Boryslaw et son 

 Traitement Industriel. 



