EQUIVALENTg. 



of the rocks of Rirkdale cavern, and he refers to an under 

 part of it, which considerably resembles the geodiferous 

 limerock. 



18. Third graywacke. Pyritus shale and grit. This stra- 



tum seems to be in the same situation with the Umestone 

 beneath it, in respect to foreign equivalents. Perhaps it 

 may agree with the mimophyre of Brongniard. See the 

 profile section at the top of the map. 



19. Oolitic rocks. Our silicious fields of limestone on the 



Allegany Mts. may be the jura limestone. Oolite the 

 same. No chalk discovered in North America. 



20. Plastic clay. 8ame, 



21. Marly clay. London clay. 



22. Marine sand. Same, and hagshot sand. 



23. Shell marl. Same. 



24:. Volcanic rocks. Same^ and hasaltj trachyte and traj^ 

 rocks, 



25. DiLuvioN. Same. 



26. Ultimate diluvion. Same in Europe, though never pub- 



lished by any geologist but American. 



27. Post-diluvion. Same, but improperly called alluvion 



by some ; as this is a generic name. 

 fiS. Analluvion. Same in Europe, though never published by 

 any geologist but American. 



N. 1st. DeLuc seems to have had an indistinct view of our 

 ultimate diluvion and analluvion, when he introduced the name 

 Geest. 



N. 2d. It may be adopted as a general rule, that European 

 strata present in many respects, more recent characteristics 

 than their equivalents in America. There bituminous coal, 

 for example, occupies the place of the Pennsylvania anthra- 

 cite, &c. &c. 



