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progression of temperature downward. The access of external 

 air is also important ; the temperature of the air in winter at the 

 bottom of this well must be very low ; the lateral perforation of 

 this low temperature ought to be traced ; the law of progress of 

 temperature from the surface downward in this special locality 

 should be ascertained. So that the question of explanation be- 

 comes very complicated. 



Dr. Bryant presented a number of valuable specimens of natu- 

 ral history which he had collected in the Bahama Islands during 

 the last spring. He remarked that all the islands seem to be 

 composed of the same limestone, which the sea is gradually un- 

 dermining and washing away. He found no fossil shells except 

 of such species as now exist on the islands. The soil in many 

 places contains great quantities of oxide of iron ; also incrusting 

 the rocks in various places, the presence of which substance he 

 was at a loss to account for. It is generally believed and stated 

 that the gulf weed is seen always floating, and that the place of 

 its growth is not known ; he had found it growing all over the 

 Bahamas, attached to rocks like any other sea-weed. He pre- 

 sented many fine specimens of Gorgonia, and of sponges, of the 

 latter of which many varieties were shown growing together. 

 He found no fringing coral reef in the part of the Bahamas vis- 

 ited by him, though he had sailed many hundred miles among 

 them in various directions. He presented a large collection of 

 plants and fungi, and of land and marine shells and Crustacea — 

 also a large and valuable collection of fishes, containing many 

 rare and some new genera and species. 



Mr. Putnam observed, in regard to the fishes, that they pre- 

 sented a remarkable resemblance to the fauna of the Sandwich 

 Islands. 



Prof. Rogers offered an explanation of the occurrence of the 

 ferruginous matter with carbonate of lime, by reference to the 

 ferruginous sand over marl beds, so common in the Southern 

 States ; in this there are many fossil specimens in which the 

 petrifying agent is oxide of iron. This would suppose a state of 

 things in the Bahamas, when the iron was there, very different 

 from what is seen now ; a very slight proportion of iron, how- 



