2 G(',olo(j!j of tlic Gold Fieldx of Brithh. (riiiano. 



at that time Acting Commissioner of Mines, now Surveyor-General in 

 the colony of British Honduras. 



In the journeys on tlie Lower Essequibo, Groete Creek and Cuyuni 

 River districts, Mr. C. Wilgress Anderson, F.G.S., F R.G.S., accom- 

 panied me and made the necessary route surveys. My thanks are due 

 to these gentlemen for the great assistance they have rendered, both 

 during the journeys and in the pi-eparation of the various reports and 

 maps. Mr. R. Ward, Agricultural Assistant in the Department of 

 Science and Agriculture, accompanied us during most of our journeys, 

 and rendered much assistance in the collection of rock specimens, and 

 by making visits to places which, on account of lack of time, were 

 otherwise inaccessible to the expeditions. 



The accounts of the structural geology of part of the Upper 

 Demerara River and of the Mazaruni River above Sororieug, are by 

 Mr. Perkins ; while I am indebted to Mr. Anderson for those of the 

 Cuyuni River above Devil's Hole, of the Venezuelan and Brazilian 

 boundaries districts, and of the Berbice River. 



Much use has been made, during the expeditions and the preparation 

 of this account, of the Geological Reports of Messrs. Brown and Sawkins, 

 of publications relating to the geology of Omai, by Dr. Emil E. 

 Lunowitz, Ph.D. ; of the " Geologisch-bergmiinnische Skizzen aus 

 Surinam,'' by Dr. G. C. du Bois ; of the "Guide Pratique pour la 

 recherche et I'exploitation de For en Guyane Frangaise," by Dr. Levat, 

 and of the published papers by Mr. E. G. Braddon. Where feasible 

 my obligations to them are noticed in the text. 



I am also under obligations to the Indians and others who were 

 with the expeditions as boat-hands, and especially to Captain George 

 Cozier, who accompanied the expeditions to the Essequil)0 and Potaro 

 Rivers, to the Mazaruni and Puruni Rivers, and to the Cuyuni River as 

 steersman and boat-captain. During these expeditions he attained 

 considerable knowledge of the work of geological reconnaissances, and 

 his skill as steersman, his knowledge of the topography of the rivers, 

 and his energy and devotion to his work proved of high value. 



I have received much assistance in making the numerous analyses 

 and assays required from John Williams, Esquire, F.C.S., Chief 

 Assistant Analyst in the Government Laboratory. 



My special thanks are due to Dr. J. Harris Teall, F.R.S., the 

 Director-General of His Majesty's Geological Survey of Great Britain, 

 for the great assistance he gave me by examining many of the micro- 

 scopic slides prepared from the rocks of the North-Western and of the 

 Essequibo-Potaro districts. 



G. F. Franks, Esquire, M.A., F.G.S., of Queen's College, has from 

 time to time assisted me by examining microscopical slides prepared 

 from the samples of rock collected during the expeditions, and l)y 

 reading many of the pi-oofs of my reports. 



Acting upon the experience recorded by Messrs. Brown and Sawkins 

 in their Reports on the Geology of British Guiana showing that it 

 was practically useless to attempt the examination of the auriferous 

 districts of the Colony except during the drier i)arts of the dry seasons, 



