i$6 On the Natural Causes which operaie 



channel will cease, and that the stream may continue to flow 

 •for innumerable ages with but trivial alterations in its course. 

 This is the true reason why *we do not now see streams 

 forming valleys, the work having been long since accom- 

 plished by the channels being reduced to their lowest de- 

 scending level : and only by the bursting out or' a^ new 

 spring head, in a situation distant from any other stream, 

 could we now practically observe the progression of falls 

 and lakes into valleys and flats, in the manner described. 

 The progress of the stream flowing from such a new 

 spring head would most assuredly establish the truth of 

 every thing I have already stated. For it cannot be 

 doubted that every stream must originally have formed its 

 own channel ; and it must be equally obvious, that when 

 first left to find its ov n way over a great inequality of sur- 

 face, it must frequently have precipitated down declivities 

 into hollows, out of which it could have no other exit than 

 by swelling into a lake, until the water rose over the level 

 of the lowest ground which bounded the hollow, 



In many cases a valley commences immediately at the 

 source of a stream, just opening there and gradually deepen-? 

 ing downwards to the lower end, where, questionless, the 

 Stream once fell, and where the cutting of the valley com- 

 menced ; and this form, of being shallow at the upper and 

 deepening down to the lower end, where the fall of the 

 Stream first began to act for its formation, is also common 

 to numerous valleys, more especially those near the spring 

 heads ; and while it perfectly accords with the action of the 

 stream, it is utterly irreconcileable with any other explana- 

 tion. Nothing, too, is more usual than the intersection 

 of one valley with another at the confluence of two streams; 

 and in every such instance the angle of intersection of the 

 valleys and streams is acute above and obtuse below, and 

 the two streams invariably meet on precisely the same level. 

 All this would naturally and necessarily result from the 

 streams forming their own valleys and channels, but it is 

 utterly impracticable to assign the most remote probable cause 

 for the same union, and unison of effects by any other na- 

 tural means. 



