vill CONTENTS. 
ARTICLE IX. 
Description of Some New Fossil Shells from the Tertiary of Petersburg, Virginia. By Henry C. Lea, . 
ARTICLE X. 
Description of New Fresh Water and Land Shells. By Isaac Lea, 
ARTICLE XI. 
Observations made in the Years 1838, ’39, 40, ’41, 742, and ’43, to determine the Magnetical Dip and 
the Intensity of Magnetical Force, in several parts of the United States. By John Locke, M.D., 
Professor of Chemistry and Pharmacy in the Medical College of Ohio, . : . ' ‘ 
ARTICLE XII. 
Observations of the Magnetic Dip, made at several positions, chiefly on the south-western and north- 
eastern frontiers of the United States, and of the Magnetic Declination at two positions on the River 
Sabine; in 1840. By Major James D. Graham, of the United States’ Corps of ‘Topographical 
4 . ° . . 
Engineers, ; 
Donations to the Library and Cabinet, ‘ ‘ ; 
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