162 ON THE REVOLUTIONS 



of every degree of wideness, from the narrowest ravine to the 

 most open vale. 



All this progress, or at least great part of it, being perform- 

 ed by successive starts, each of which, while under water, pro- 

 ducing a tremendous wave ; the mass, in rising, would be re- 

 peatedly exposed to these diluvian torrents, some formed by 

 itself, and some by neighbouring elevations, so as at last, after 

 long exposure to agents, partly diluvian and partly diurnal, it 

 would arrive at its present situation and condition. 



In consequence of the diversity of these elevations in place 

 and in magnitude, acting upon substances of every sort, an 

 endless diversity of effect would be the result. In some cases 

 a rent, in consequence of the locality of the heave, would be 

 rendered both large and deep in the middle, while it remained 

 nearly closed at both ends. Water, therefore, could not flow 

 through it without stagnating by the way, and thus a lake 

 would be formed, the depth of which might be very great in 

 the middle, though its extremities were shallow. This applies 

 to the formation of the lake of Geneva, either before or since 

 the passage of the granitic blocks. It is applicable also to 

 all lakes which occur m alpine or rocky districts. It will ap- 

 pear in what follows, that an account no less satisfactory may 

 be given on other principles of those which belong to alluvial 

 countries. 



An example of the relative changes among rocks, produced 

 by motions of this sort, occurs in the mass on the coast of Ber- 

 wickshire, with which we have been so much occupied in a for- 

 mer meeting, as affording a display of the convolutions of the 

 strata. Upon this coast, the killas and sandstone meet on the 

 East near Eyemouth, and on the West in the parish of Cock- 

 burn spath, at the Siccar Point, where the junction is beautiful- 



