243 



deposition the whole basin was low, subsided gradually and 

 was afterwards raised. If this had not been the case, marine 

 fossils would probably have been found, from its proximity to 

 the sea. This bluff is two hundred feet high and contains land 

 and fresh water shells and mastodon bones. 



Mr. Desor remarked, that it was interesting to observe the 

 influence which geological causes had had in fixing the localities 

 of cities on the Mississippi and Ohio. The terraces of the 

 upper Mississippi are very low and exposed to inundations, so 

 that towns can only be built on the bluff beyond. This limits 

 the location of towns to those bluffs near the river. On the 

 Ohio, on the other hand, the terraces have been elevated to the 

 height of fifty, eighty, or one hundred feet, and the cities are 

 built upon this alluvial foundation, having the drift behind them ; 

 in the Mississippi they are built on the drift itself, so that the 

 banks of the Ohio offer the more eligible situations for settle- 

 ment. 



Dr. Storer addressed the Society on behalf of the Journal. 

 He urged upon the members its value and importance as a 

 means of extending the influence of the Society and pro- 

 moting the interests of Science. He hoped that members 

 would give evidence of their continued interest in the So- 

 ciety by making an effort to increase the subscription list, 

 novv^ that the sixth volume v^as just commencing. 



Robert Briggs, Jr. was elected a member of the Society. 



February 20, 1850. 



The President in the Chair. 



Present, twenty-nine members. 



Dr. C. T. Jackson read an analysis and description, and 

 exhibited a specimen of Vermiculite from Millbury, Mass. 

 The analysis was made by Mr. Richard Crossley. Dr. 

 Jackson exhibited to the Society the singular property 

 which this mineral has when heated, of swelUng to many 



