INTERMEDIATE EROSIONS. 125 



9. A similar bed on the same river, at Chester village (now called Huntington). 

 See No. 11 of this paper, ia hypozoic rocks. 



10. A similar bed on the east branch of this same river, four miles above Chester 

 village. See No. 12, in hypozoic rocks, of this paper. 



4. Some cases of erosion described in this paper appear to have been mainly 

 intermediate, as to the time of their formation, between the antediluvial river beds 

 just enumerated, and the earliest formed in the hypozoic rocks. 



I would not undertake to decide positively how many times this continent, or 

 large portions of it, may have been beneath and above the ocean. But I do not 

 see how we can escape the conclusion that it must have been submerged at least 

 three times. During the Silurian period we must admit its submergence; and 

 during the carboniferous period, certainly large portions of the surface must have 

 been above the waters to allow a gigantic growth of plants. The triasic, oolitic, 

 and cretaceous deposits, must have been made on surfaces beneath the ocean. The 

 tertiary strata seem to have been formed chiefly in estuaries, and with dry land in 

 the vicinity, which indicates a second emergence. The evidence that the same 

 surface was beneath the waves during the deposition of drift, has been presented 

 in the paper on Surface Geology : and we have the proof beneath our feet of the 

 third emergence of our country during the alluvial period. 



During all these vertical movements, erosions of the surface must have been 

 going on. I have referred to some examples of this work, commencing at the 

 earliest period, or during the first emergence and drainage of land: and also some 

 cases referable to the last upward movement. The following cases seem most 

 probably to have been produced at an intermediate period, but precisely when (as 

 to geological sequence rather than chronological dates), I am unable to determine. 



1. The Proctorsville gulf, in Cavendish, Vermont. See the description in this 

 paper, No. 14, in hypozoic rocks. 



2. Gorge on Delaware river, from Port Jervis to Narrowsburg, in Pennsylvania. 

 A very old erosion, perhaps among the oldest. 



3. The canons of the southwest, described in this paper. Very old. 



4. Gorge on New river and the Kenawha, in western Virginia, in coal sand- 

 stone. No. 20, in fossiliferous rocks, of this paper. 



5. Gorges in New South Wales, Australia, in sandstone. Nos. 16 and 17, in 

 fossiliferous rocks. 



6. Natural bridges in Virginia. 



7. Do. on the Euphrates, near Diadeen, in Armenia. 



8. Do. on Dog river, in Mount Lebanon. 



9. Gorge on the river Kavendooz, in Kurdistan. 



10. Wady el Jeib, in Palestine. 



11. Via Mala, in Switzerland. 



12. Defile of Karzan, on the Danube. 



13. Old river bed, east side of Mettawampe, in Massachusetts. 



14. Gorges through trap, on the Columbia river and its tributaries. 



The grounds on which I refer these cases to a period intermediate between the 



