hi I he Production of Valleys. lQ^ 



rales do not always follow tlie lowest ground ; that i^, the 

 natural fall of the country. This looks like a mere qiiihble 

 on the word ali^ai/s. My expression was, " that we.uiay 

 always be assured that the course wljich the stream has 

 -taken is ihe lowest descent of the country in that tiirection." 

 nor do I conceive it possible to state a more correct, or a 

 more widely extended general truth. The geti-era/ direction 

 of excavated valleys and their streams is, indeed, univer- 

 sally along with the common f;dl of the country ; and it is 

 a most important fact in the main question, for it both il- 

 lustrates and confirn)s the excavation of ihevale^by streams; 

 seeing that the excavation has contiwuailv proceeded in the 

 same direction with the natural fall of the country, and, 

 consequently, with the original course of the streams. In- 

 deed, so substantially true is the proposition which I ad- 

 vanced, and which Mr. Farey finds it so necessary to his 

 f)urpose to deny, that there is an absolute physical impos- 

 sibility of streams, when left to themselves, flo'wing in any 

 other direction than the lowest fall of the country over 

 which they iiave to flow. To suppose otherwise, would 

 require them either to ascend, or instinctively to avoid de- 

 scending, in some parts of their course. 



Mr. farey also asserts, " neither is it true that, in every 

 instance, the angle of intersection of valleys and streams 

 is acute above and obtuse below, or that two streams inva- 

 r'lubly n)eet on precisely the same level." Here, asrain, if 

 the denials have any meaning at all, it is mere quiljbli,ng 

 on the words in italics. Has Mr, Farey ever seen an in- 

 stance where the intersections spoken of occurred with 

 angles acute below and obtuse above : that is, where the 

 .streams coalesced by meeting each other? Or where has 

 he seen, at the confluence of twx) streams, the one falling 

 from a height into the other? And yet, if he has seen both, 

 and that very frequently too, what must I think of hiscou- 

 cealing .some of the most material general truths in the 

 question r lie may, indeed, have &een, and I suppose they 

 are what he alludes to, a tew instances of a trivial rill 

 trickling over a bank, at right angles into a stream; but 

 Would he balance such instances against those to which I 

 reierred, and vvliieh are as numerously disseminated over 

 this and every other country as are the streams themselves? 

 'J'he triuh assuredly i-, that these olijcctions were con- 

 venient hir putting aside a siring of general facts and rea- 

 4ornng, w Inch the most ingenious and artful hypoihesist, 

 who denies the action of the streams, dares nt)t either di- 

 «ectly oppose or venture lo illustrate, by laiily lULeting thp 

 N 3 i'taelical 



