412 Revieivs — Colonel Greenwood's Bain and Rwers, 



V. — Eain and Eivers ; or, Htjtton and Platfair against Ltell 

 AND ALL Comers. By Colonel Greenwood. Second Edition. 

 London : Longmans, 1866. 



WE scarcely know what to say of this extraordinary book. That 

 it contains many happy theoretical hits cannot he denied, 

 and though the author's propensity for humourous digressions con- 

 tinually disturbs the grave attention of the reader, some portions 

 are well reasoned and clearly expressed. One of his great objects 

 seems to be to attack Sir Charles Lyell, Professor Sedgwick, 

 and other great founders of the science of geology ; and while he 

 accuses Humboldt of concealing the laws of Nature "behind the 

 double veil of Greek and Latin," he scarcely writes a page without 

 introducing a Latin sentence or quotation. Still he must be credited 

 with the merit of having been the first, of late years, to give to the 

 world (in the " Tree-Lifter," in 1853, and " Eain and Eivers," 1857,) 

 a clear exposition of the subaerial theory of denudation. Professor 

 Jukes acknowledges this in his " School Manual of Geology ;" 

 and it would only be an act of justice if other subaerialists were 

 to make more frequent reference to the author. It would likewise 

 be well if they rendered their speculations more consistent by 

 imitating Colonel Greenwood in laying the main stress on rain and 

 not on rivers, for it is obvious that if rains cannot act effectively 

 in a state of general dispersion so as to produce the gently-sloping 

 declivities which characterize the majority of hills and valleys, 

 torrents and rivers which (as the Colonel admits) act on lines 

 only, could not have given rise to the general form of the ground. 

 As many who have not read " Eain and Eivers " may like to know 

 how far its author has forestalled the more recent advocates of 

 phvialism, we shall give a number of quotations from his work : — 



" No marine current could make a single channel sloping from a 

 height to the sea ; still less the myriads on myriads of dry upper 

 valleys which ramify in all directions, from all river valleys, 

 through and to all sides of the tops of all elevations, whether high 

 or low." " Soil is rotted subsoil," and " is in constant formation 



over the entire surface of the earth Eain produces a denudation 



of an enormous breadth of hillside. .... Eain may be said to 

 form hills as well as valleys Valleys exist only in the disso- 

 lution of hills A stream running through ridges, large or 



small, is the simple consequence of the differing hardness of the 

 ground through which it runs. In all cases a stream cuts for itself 

 a narrow channel, the depth of which is determined by its hardest 



part But the wash of rain digs down where the ground is 



soft and leaves hills or ridges where it is hard. And as a stream 

 cuts through a hard stratum, say the North or South Downs, the 

 wash of rain is scooping out two lateral valleys heJund it, that is a 

 valley behind each side of the gorge and ridge, as in the Weald clay. 



The debris of these valleys is carried off by the lowering bed 



of the river. A ridge is then developed, and the river runs through 

 a gorge in the ridge Directly as the softness, is the width. 



