Intelligence and Miscellaneous Articles. 75 



scured their specific characters, thus rendering their determination 

 extremely difficult, Dr. Duncan found it necessary to thoroughly 

 examine their different varieties of mineralization, and to compare 

 their present condition with the different stages in the decay and 

 fossilization of recent Corals as now seen in progress. Thus the 

 author was enabled to show the connexion between the destruction 

 of the minuter structures of the Coral by membrane decomposing 

 and certain forms of fossilization in which those structures are im- 

 perfectly preserved ; and he likewise stated that the filling-up of the 

 interspaces by*granular carbonate of lime and other substances, as 

 well as the induration of certain species, during a "prefossil" and 

 " post-mortem" period, gave rise to certain varieties of fossilization, 

 and that the results of those operations were perpetuated in a fossil 

 state. 



The forms of mineralization described by Dr. Duncan are — 

 (1) Calcareous; (2) Siliceous; (3) Siliceous and Crystalline; (4) 

 Siliceous and Destructive; (5) Siliceous Casts; (6) Calcareo- 

 siliceous ; (7) Calcareo-siliceous and Destructive ; (8) Calcareo- 

 siliceous Casts. 



In describing these forms, especial reference was made to those in 

 which the structures were more or less destroyed during the re- 

 placement (by silica) of the carbonate of lime which filled the inter- 

 spaces, and during that of the ordinary hard parts of the Coral. 



In explaining the nature and mode of formation of the large casts 

 of calices from Antigua, the author drew attention to the fact that 

 the silicification is more intense on the surface and in the centre of 

 the corallum than in the intermediate region ; and, when examined 

 microscopically, it could be seen that the replacement of the carbo- 

 nate of lime began by the silica appearing as minute points in the 

 centre of the interspaces and of the sclerenchyma, and not on their 

 surface. In conclusion, the relation of hydrated silica to destruc- 

 tive forms of fossilization was discussed, together with the influence 

 of all the forms enumerated above in the preservation of organisms, 

 and as one cause of the incompleteness of the geological record. 



IX. Intelligence and Miscellaneous Articles. 



REMARKS ON THE DISTILLATION OF SUBSTANCES OF DIFFERENT 

 VOLATILITIES. BY M. CAREY LEA. 



SOME experiments which have been recently published by M. 

 Berthelot recall to me a similar and remarkable case which 

 attracted my attention several years ago. 



M. Berthelot distilled 92 parts of alcohol and 8 of water, and 

 found that the distillate at the beginning, middle, and end of the 

 operation contained equal quantities of water and of alcohol. 



He distilled also a mixture containing a large quantity of sulphide 

 of carbon and a small quantity of alcohol, and found that the least 

 volatile body, the alcohol, passed over with the first portions of the 



