in the Production of Valhys. \Ql 



of iTiobility of all the loose materials of our ean.li ; and that 

 iiisteaLl of wandering out of Nature after hvpothetical 

 snigmas, to explain the mightv changes which the exterior 

 and interior of our globe liave every \\'here undergone, we 

 have only to appreciate, justly, the incessant, varied, and 

 powerful action of that fluid, in order to obtain the most 

 rational, simple, and natural elucidation of ail the general 

 and principal phEsnoniena in geology. That branch of the 

 subject, however, which relates- to the action of fresh water 

 streams ilov/ing over unequal and inclined surfaces having 

 experienced direct and decided opposition, [ must ao^ain so- 

 licit the use of a few pages in your valuable ref)osifory. 



The objection?, indeed? to which I allude, are hardly 

 entitled to any reply: for they in no respcci invalidate, and 

 scarcely at all advert to, the general question on its own 

 broad basis, or meet the vast chain of general and harmo- 

 nizing facts, upon which the whole merits of the casehinge. 



These were expressly staled to be : — the elevated situation 

 of the sources and sprinirfieads of all streams, which gives 

 them an easy and natural How over the countries out of 

 which all valleys have been excavated, — the most important 

 and material fact in the whole question ; — the present slopes 

 at the lower ends of most valleys, where the streams must 

 originally have had a fall corresponding with the pre- 

 sent depths of the valleys; — the mechanically abradmg 

 forces of the streams at these fails, and which are an>ply 

 sufficient, with the occasional aid of flooded torrents, to 

 liave effected the excavation of the valleys; — the obvious 

 certainty that, were the valleys again lilled up, the streams 

 would still continue to flow wx nearly their present direc- 

 tions, forming in that case a succession of lakes and water- 

 falls, similar to what must have existed before the valleys 

 were excavated ;— that at the falls, produced by the lillinor 

 up of the valleys, the streams would immediately com- 

 iTience the excavation of other valleys, in all respects similar 

 to those of our present ones; and, in line, that the streams 

 themselves are the only agents in nature that can possibl-y 

 have accomplished such a system of uniform efleets as ex- 

 cavated valleys display throughout every country. 



It was added, ihal all the exislins phenomena, in the 

 present courses of strean)s, strictly corre.-pond with the fore- 

 going order of things: — namely, the jSrescnt direction of 

 valleys, which every where so regularly falls in with the na- 

 tural descent of the country-, precisely as the streams must 

 originally have done before the valleys were excavated, and 

 would do again were they again filled up; — the unbroi;cii 



chain 



