J. D. Dana — Deep troughs of the Oceanic depression. 195 



Zealand range and that of the east coast of North America ; 

 and also that of South America (which is continued across the 

 ocean to Scandinavia) ; also (2) between the trend of the foot 

 of the New Zealand boot with the Louisiade group and New 

 Guinea farther west, and the mean trend of the islands of the 

 central Pacific both south and north of the equator, and also 

 that of the north shore of South America. These are a few 

 examples out of many to be observed on the map. 



(5). The relatively shallow- water area which stretches across 

 the North Atlantic from Scandinavia to Greenland — the Scan- 

 dinavian plateau, as it may well be called — is continued from 

 these high latitude seas southwestward, in the direction of the 

 axis of the North Atlantic (or parallel nearly to the coast of 

 eastern North America and the opposite coast of Africa), and 

 becomes the " Dolphin shoal." 



It may be a correlate fact in the earth's system of features 

 that a Patagonian plateau stretches out from the Patagonia 

 coast, or from high southern latitudes, in the direction of the 

 longer axis of the Pacific, and embraces the Paumotu and 

 other archipelagos beyond.* 



The above review of the Earth's physiognomy, if accom- 

 panied by a survey of the map, may suffice for the main pur- 

 pose here in view : to illustrate the general truths — that sys- 

 tem in the feature-lines is a fact ; that the system is world- 

 wide in its scope ; and — since these feature-lines have been suc- 

 cessively developed with the progress of geological history — 

 that the system had its foundation in the beginning of the 

 earth's genesis and was developed to full completion with its 

 growth. 



2. Facts Bearing on" the Origin of the Deep-sea 



Troughs. 



In treating of this subject, the facts from the vicinity of 

 volcanic lands that favor a volcanic origin are first mentioned ; 



* As parallelisms may have importance that is not now apparent, I draw atten- 

 tion to one between the Mediterranean Sea that divides Europe from Africa, and 

 the West India (or West Mediterranean) sea that divides North from South 

 America. Both have an eastern, middle and western deep basin. Their depths 

 (see map) in the East Mediterranean, are 2170, 2040 and 1585 fathoms; in the 

 West Mediterranean (the three being the Caribbean, the West Caribbean or 

 Cuban, and the Gulf of Mexico), 2804, 3428 and 2080 fathoms. Further, in each 

 Mediterranean Sea, a shallow-water plateau extends from a prominent point 

 on the south side, northward, to islands between the eastern and middle of the 

 deep basins ; one from the northeast angle of Tunis to Sicily, the other from 

 the northeast angle of Honduras to Jamaica and Haiti, the two about the same 

 in range of depth of water. And this last parallelism has its parallels through 

 geological history, even to the Quaternary, when the great Mammals made mi» 

 grations to the islands in each from the continent to the South. 



