151 



names 



ml forms. One of these, 



£uch the cells were j^SSTu ^T^SK? oT T the 

 Cyanophyceae, and differed from the Alga in N'hangellite in 

 several particulars, thongh the arrangement of the cells in the 

 co onies was similar to that in the small colonies seen in N'han- 

 feetite. In those deposits which were formed chiefly from 

 gela inous Algae, Bertrand regards the substance derived from the 



TZ i l !£ *l UiVing b 1 eC ° me infiltrated b y bitumen. In other cases 

 subarl, * £ Hi? T les * ab undant he attributes a great part of the 

 form f™ * tbe deposition of humic compounds in gelatinous 

 torm from the water in which the Algae grew. 



t» Tw C 2? ClU8 i° n to be drawu from the examination of N'hangellite 



n,l fl !! 5 G 8ubs . tance h ™ bem derived, chiefly at any rateffrom 



asses of a gelatinous Alga, and that chemical changes must have 



VVh h P f m th ® mucilage, giving it a bituminous character. 

 fnrnttlZ Tlu acM *?fy have contributed in some degree to the 

 iormation of the substance remains to be proved, but that ex- 

 traneous petroleum should have done so is entire y improbable 

 Hence the occurrence of N'hangellite gives no evidence to* he 

 presence of petroleum in the district in which it is found, but in 

 a permanent, lake-region similar deposits may well have been 

 formed from time to time, giving rise ultimately to fossil deposit 

 ot bitumen or strata containing petroleum. opposite 



X S;7 REP0RT 0N A SAMPLE OF N'HANGELLITE 

 FROM INHAMBANE, PORTUGUESE EAST AFRICA. 



Sir Boverton Redwood. 



* 



greater part of the sam 



thickness 



pieces about one-eighth of an inch thick. Both were elastic. The 

 tninner pieces were translucent and of a brown colour by trans- 

 mitted light. The thicker pieces on being cut through appeared 

 to be fairly uniform throughout, but the weathered surfaces 

 seemed to be less elastic than the interior. The thinner pieces 

 showed signs of lamination and could be snlit into lav*™ 



Dertrana ec "eaauit, Jfiia bibractensig et Ie boghead d'Autun Bull Soc 

 d Hhst Nat. (TAut,,,,, 1892; Bertrand, Ls Kerosene Shale de la NoureUe-GaJlc 

 du bud, ibid. 1896 ; Renault. Les Organismes dea Cannels, Bull. Museum d'Htit 

 Aiat., Pans, 1898 ; Bertrand, Kerosene Shale de Megalong Valley, Ann Sor Gtnl 

 du Nord, Lille, 1900 ; Bertrand, Charbons gelosiques et charbons \™\ n Z 



papers 



Paris, 1901 : and 



\ 



