ve 
ii: il 
The Glacial Theory of Prof. Agassiz. 359 
Mount Jura rises at some points to the height of 5,000 feet* above 
the sea, and 3,500 above the great valley of Switzerland on its south 
_ side. The Alps run parallel to Jura at the distance of fifty miles, and 
We = « their higher summits have an elevation varying from 11,000 to 15,000 
‘A 
¥ 
’ primary rocks, granite, 
feet above the sea ; but the northern skirts of the chain are a great deal 
lower, and their diated from Jura scarcely exceeds thirty miles. The 
following diagram will sees an idea of their relative position: 
~MVBP, The chain of ‘ Fig. 8. wet 
the Alps extending north- re 
east and southwest. 
11,22, 3, The chain of 
Jura, running parallel to 
the Alps. 
SS, The great valley of 
Switzerland separating the / 
two chains. & 
‘G, The lake of Geneva; Sy 
N, the lake of Neuchatel. 
' The Alps consist of 
gneiss, &ec., in the centre, 
flanked by secondary. Ju 
ra consists of different for. 
mations of limestone, all bling to the oolitic series. 
“The two chains, in distancé, bearing, and position, may be compared 
to the Ochil and Pavia hills. If we suppose the Ochils to be 
twice, and the Lammermuirs six times as high as they are, and the 
valley between them, constituting the basin of the Forth, to be three 
or four times as deep as it is, we shall have a pretty good idea of the 
physical features of the district under consideration. 
“Now the fact which has so long exercised the ingenuity of geologists 
is this. Hundreds‘of huge fragments of primary rocks, distinctly re- 
cognizable as portions of the Alps, are found perched on the southern 
declivities, or resting in the interior valleys of Jura, forty or fifty miles 
from their native lodality' ; and geologists have been perplexed to dis- 
cover by what agency these erratic blocks have been transported across 
the great Swiss valley, and placed in the singular situations where we 
them. The magnitude, external appearance, and distribution of 
pth tian et ae Worthy of notice. 
Bes 
* The measures are always in French feet, which may be converted in Eng 
lish by adding one fifteenth. 
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