THE ATLANTIC SYSTEM OF MOUNTAINS. 369 



Then there was a sag along Hudson river, which may indicate the course of another 

 break at the lowest part of the mountains just as the other fault shows itself along the 

 Kanawha where the ge-anticlinal ridge is manifest. 



Concerning the great valley, Lesley remarks that there is "an unbroken rim of Que- 

 bec and Laurcntian from Georgia to the extreme eastern end of Canada, contrasted 

 strongly with the plateau of the coal, commencing in Alabama and cut off square by 

 the Hudson, the open valley of the Lower Silurians everywhere keeping the two systems 

 apart." 



In Europe, physical geographers refer the Alps and Jura mountains to different sys- 

 tems, characterized by features similar to those just indicated between the two portions 

 of eastern America. The Alps correspond to the Atlantic, the Jura to the Appalachian, 

 and the valley of Switzerland, prolonged into Bavaria and Moravia, to the great Appa- 

 lachian valley. A section from Italy to the Rhine valley would be very much like the 

 one in our country from eastern Virginia across to Cincinnati. 



The Alps are composed of crystalline rocks centrally, with Carboniferous, Mesozoic, 

 and Cenozoic groups corresponding to each other upon both sides. The structure is 

 fan-shaped, but explained by supposing it to have been an anticlinal arch like a loop 

 overhead, long since broken down and removed by denudation. The newer groups are 

 arranged in close synclinal troughs, the older nearest the central crystallines, and con 

 sequently sometimes resting upon the newer ones by a species of inversion. The rocks 

 of the Jura are largely Mesozoic, and are the best known exhibitions of the particular 

 belts called for that reason the Jurassic. The Alps and Jura of America are there- 

 fore very much like their prototypes in Europe, in all essential particulars. 



Authors have variously compared the American with the Swiss mountains. Guyot* 

 says that the western portion is like the Jura, — adding that "there is one feature which 

 distinguishes it [the Appalachian] from the Jura : it is the well-marked division into 

 two longitudinal zones of elevation," or the ones distinguished above as Atlantic and 

 Appalachian. The same author includes the Adirondack mountains with the Appa- 

 lachians. J. D. Whitney t speaks of the Cordilleras (Pacific highlands) as like the Alps, 

 and the Appalachian (Atlantic highlands leaving out Adirondacks) as like the Jura. 

 The attempts of these distinguished authors to correlate our mountains with the Alps 

 and the Jura, strengthens our conviction of the propriety of using special names for 

 the chains corresponding to them so perfectly as do the two divisions mentioned south 

 of the St. Lawrence. 



That the name Appalachian is commonly used to include both these systems, is 

 undeniable. My suggestion is, that we adopt an improved terminology, at least in 

 geological treatises. Two or three considerations maybe noted, i. The desire for 

 a single name to express the mountains along the eastern slope of the continent has 

 led to the undue extension of the name Appalachian. But it should be remembered 

 that, if it is used appropriately, it must include the Adirondacks and Labrador moun- 



* Amer. Jour. Scie/ice, ii, xxxi, p. 166. f W.illicr's Physical Atlas. 



VOL. III. 48 



