of the London mid Hampshire Basins, ^x. 115 



where its beds of sand, or more cohesive parts, have resisted 

 the erosive power,) and is thinned out upon the chalk. The 

 chalk next, being a stratum of greater induration, and pre- 

 senting a less destructible fracture-edge, breaks down in an 

 abrupt escarpment, where ic has suffered disturbance enough 

 to ensure its entire demolition ; but where not so broken up, 

 continues spreading over a large surface, and though ci'acked 

 and furrowed in the same order as the other strata, remains 

 in its place, dipping north and south under its upper cover- 

 ings. Leaving the basset edge of the chalk, the act of denu- 

 dation is found to have brought out the strata beneath, in 

 ridges or furrows, according to the greater or less indura- 

 tion, the greater or less destructibility of their materials*; 

 abrupt escarpments or fracture-edges presenting themselves 



in 



* It is delightful to meet with confirmations of the community of cha- 

 racter of diluvian abrasion or denudation in all parts of the globe. The 

 following quotation will show, that Australia possesses the same phenomena 

 of surface as we have been here descanting on. 



*' In this county (Argyle) you have several excellent samples of that 

 singular appearance sometimes presented by the land in its state of nature, 

 exhibiting, as you would suppose, the most striking evidences of former 

 cultivation, in the regularly laid-out ridges apparently produced by the 

 plough, which here and there intersect your path. I have seen twelve at 

 least of these ridges, all contiguous and extending in length for two hun- 

 dred yards and more, so evenly proportioned, that I do not think above a 

 foot diiference could be detected in any of their breadths ; whilst I could 

 almost have protested that I could perceive the very |)lough landings, and 

 count their number in the ridges, which are usually about ten or twelve 

 feet broad. The same appearances are more plentifully and strikingly 

 portrayed at Bathurst and at Hunter's River. They occur always on 

 gentle declivities, where there is a tenacious subsoil with loose superstrata, 

 and are doubtless produced by the rain-torrents ; but how this great re- 

 gularity in their breadth is effected, is a problem of difficult solution. Here 

 too I have witnessed, upon the tops of ridges, extensive beds of water- 

 sand and water-gravel, mixed with fragments of shells, presenting the 

 identical apjicarances yon will observe upon the banks of rivers, or upon 

 sea beaches." — Cuiininghatus New South Wales, vol. i. p. 116. 

 . These are the remarks of an acute observer, unincumbered with geolo- 

 gical prejudice, but falling nevertheless into the errors of false induction. 

 And wc cannot but be struck with the similarity of the a|)pearances he de- 

 scribes to the ])ha;nomenonof the "parallel lines of Glen Roy," so ably de- 

 scribed and ingeniously descanted on by Dr. MacCnlloch, in the 4tli voknne 

 of the Geol. Trans. The simple and easy solution of the |)roblcm there 

 exhibited, is given by the universal act of abrasion. The projection of the 

 indurated lines of stratified beds, and tiie erosion of the intervening more 

 destructible parts, arc the natural effect of watery friction acting contem- 

 poraneously, and with nearly e(|nal force upon their ]H:rpendicular oc 

 oblicjue sections. The rclirf thus given to the indurateil lines of stiatifica. 

 lion, is strikingly displayed in the glens alluded to, and their parallelism 

 remarkable, because the same texture pervades all the rocks coiKcrned in 

 the formation of Glen Roy and its neighbouring valleys, and the same agen- 

 cies operated over a certain extent of surface, and ruled the formation of 



Q 2 tlie 



