NOTES TO BOOK XVIII. 695 



Prof. Playfairs elegant work, Illustrations of the Huttonian 

 Theory, (1802), so justly admired, contains many doc- 

 trines which the more mature geology of modern times 

 rejects ; such as the igneous origin of chalk-flints, siliceous 

 puddingstone, and the like ; the universal formation of 

 river-beds by the rivers themselves ; and other points. 

 With regard to this last mentioned question, I think 

 all who have read Demcs Geologie (1810) will deem his 

 refutation of Play fair complete. 



But though Hutton's theory was premature, as well 

 as Werner's, the former had a far greater value as an 

 important step on the road to truth. Many of its boldest 

 hypotheses and generalizations have become a part of the 

 general creed of geologists ; and its publication is perhaps 

 the greatest event which has yet occurred in the progress 

 of Physical Geology. 



(KA.) p. 669. I have, in the text, quoted the fourth 

 edition of Mr. LyelPs Principles, in which he recommends 

 " an earnest and patient endeavour to reconcile the former 

 indications of change with the evidence of gradual muta- 

 tion now in progress." In the sixth edition, in that 

 which is, I presume, the corresponding passage, although 

 it is transferred from the fourth to the first Book, (B. i. 

 c. xiii. p. 325) he recommends, instead, " an earnest and 

 patient inquiry how far geological appearances are recon- 

 cileable with the effect of changes now in progress." But 

 while Mr, Lyell has thus softened the advocate's cha- 

 racter in his language in this passage, the transposition 

 which I have noticed appears to me to have an opposite 

 tendency. For in the former edition, the causes now in 

 action were first described in the second and third Books, 

 and the great problem of Geology, stated in the first 



