Rocks and Minerals of British Guiana. 



Being a Catalogue of the Specimens in the British Guiana Museum, 

 collected, named, and arranged by Charles Barrington Brown 

 late Geological Surveyor of the Colony. 



jHE present article forms the first instalment of 

 the Museum Catalogue which it is intended to 

 publish serially in "Timehri," until it becomes 

 possible, by a completion of the identification of various 

 specimens and their better classification and arrange- 

 ment, to publish a catalogue in full. 



The classified list was prepared, nearly in its present 

 form, by Mr. Brown, soon after the Survey of the 

 colony was finished ; and as the collection of rocks and 

 minerals contains illustrative specimens from all the 

 various parts of the colony examined, it forms a most 

 valuable series in connection with the " Reports on the 

 Geology of British Guiana" prepared for the Govern- 

 ment by Messrs. SawkinS and Brown, the Geological 

 Surveyors. 



In these reports, the various rocks and minerals of the 

 colony have been classified into four chief groups, 

 chronologically : — 



I. — The alluvial or post-pliocene deposits. 

 II. — The sandstone formation. 

 III. — The metamorphic rocks. 

 IV. — The granitic rocks. 

 The alluvial deposits consist of a recent alluvium in 

 swampy districts and bordering small streams all over 

 the colony, apparently of a very productive nature ; of 



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