REFERENCE TO THE PLATES. 
Page 
Frontispiece. Sketcli of tlie Geology of tlie United States 
Plate 1. fig. 1. Extent of Sea in tlie Cretaceous Period in Europe. 8 
fig. 2. Extent of Sea in the Jurassic Period in Europe . 8 
Plate 2. Portions of Ammonite from Drifted Gravel ... 64 
3. Singular formation of Carbonate of-Lime .... 64 
4. Section of Strata at Cheltenham, showing the origin of the 
Saline Springs 147 
