CONTENTS. 



PAGE 



1849. By John Fletcher Miller, Esq., 

 F.R.S., F.R.A.S., &c. Communicated by the 

 Author, ...... 53 



IV. The Completed Coral Island. By James D. Dana, 

 Geologist to the American Exploratory Expedi- 

 tion, &c., &c., ...... 66 



V. Biographical Notice of Leopold Pilla, the Geologist. 



By H. CoQUAND. Communicated by the Author, 68 



VI. On the Chronological Exposition of the Periods of 

 Vegetation, and the different Floras which have 

 succeeded each other on the Earth's surface. Ac- 

 cording to the views of M. Brongniart. Con- 

 cluded from Vol. xlviii., p. 330) : — 



Fossil Plants ofthe Permian Period. — Vosgian Period. 

 — Jurassic Period. — Tertiary Period, . 72—97 



VII. Glacial Theory of the Erratics and Drift of the New 

 and Old Worlds. By Professor Agassiz ; — 



Glacialists and Antiglacialists. — Erratic basins of 

 Switzerland. — Similar phenomena observed in other 

 parts of Europe. — Points necessary to be settled ; 

 first, the relation in time and character between the 

 Northern and the Alpine erratics. — Traced in North 

 America. — Not yet settled whether any local centres 

 of distribution in America; but the general cause 

 must have acted in all parts simultaneously. This 

 action ceased at 35° north latitude; this incompatible 

 with the notion of currents. — In both hemispheres a 

 direct reference to the Polar Regions. Difficulty as 

 to so extensive formation of Ice, removed; difficul- 

 ties on the theory of Currents, the effects contrary 

 to experience of Water-Action. — Erratic phenomena 

 of Lake Superior. — The Iceberg theory. — Descrip- 

 tion of appearances at Lake Superior. — Drift : con- 

 tains mud, and is without fossils. — Example of 

 juxta-position of stratified and unstratified Drift, at 

 Cambridge. — Date of these phenomena not fully de- 

 termined, but doubtless simultaneous all over the 

 Globe. — The various periods and kinds of Drift dis- 

 tinguished. — Accompanied by change of level in the 

 Continent, ...... 97-98 



