PARALLEL TERRACES IN EUROPE.—BOULDERS IN NOVA SCOTIA. 217 
St. Lawrence. The parallel terraces that encircle this dry valley 
show the number of successive stages by which the bursting of 
the gorge took place, and are exactly similar to those engraved in 
Dr. Macculloch’s paper above quoted, in the fourth volume of the 
Geological Transactions*. 
Sir Alexander Croke has informed me, that the summits of some 
of the highest hills in Xova Scotia, being composed of slate, are 
strewed over with large blocks of granite. The present position of 
these fragments can only be accounted for by supposing them to 
have been drifted from the nearest granite districts by the same 
rush of waters that transported those described by Dr. Bigsby in 
the districts of Lake Huron and Lake Erie. And Dr. Meade, of 
* I have myself observed a similar appearance of successive terraces flanking the 
valleys of the Rhine below Basel; of the Salza, at Golling, on the south of Saltzburg; 
of the Iser, at Munich; and on the sides of many other rivers that descend from the 
Alps. These terraces are all of postdiluvial origin, and are often formed on diluvial 
gravel, and indicate either the shores of lakes that have at successive periods burst their 
barriers, and lowered their level, or become entirely dry; or, where they occur on the 
sides of rivers, they are cliffs or escarpments cut in diluvial gravel by floods of 
extraordinary height, resulting either from unusual tempests, or from the bursting 
I have just mentioned of lakes in the higher districts from which these rivers are 
supplied. 
The examples here mentioned, of the bursting of lakes, militate at first sight against 
the observation I have quoted from Mr. Weaver, that modern lakes have not a tendency 
to burst their barriers, but to fill up; still, however, he is right in his general rule, that 
such is the ordinary course of nature with respect to them. The bursting of modern 
lakes is of rare occurrence; and wherever it has happened, there is evidence of the fact, 
in its leaving parallel terraces of gravel on its ancient shores; and when we consider 
how very few the valleys are in which such terraces occur (the neighbourhood of Glen 
Roy, for example, being the only instance we know in Britain), it is obvious that these 
few cases are but rare exceptions to the general rule which Mr. Weaver has laid 
down. 
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