38 On the Anticlinal Line of the London and Hampshire Basins. 



Hopkins has not himself cbawn any erroneous conclusions from 

 this mistake, but others have*. 



The conclusions this gentleman drew from his mechanical 

 theory of fissure I had already arrived at from surface phseno- 

 niena, — the arrangements of longitudinal and transverse valleys, 

 the watershed and drainage. 



On both of his expositions of the theory of the Weald denu- 

 dation, Sir C. Lyell has given me credit for pointing out the 

 opposing river gorges in the chalk as indicative of the direct ex- 

 tension of the lines of fissure on which these gorges were formed 

 directly from side to side. I never laid much stress on this 

 point ; but when I drew attention to it, I was not aware that an 

 instance of this kind existed in its original integrity. It is the 

 more valuable, because it occurs in the westernmost part of the 

 anticlinal, and may be considered as the very experimentum crucis 

 of this theory of transverse drainage. 



The drainage of the Vale of Pewsey is brought to its lower 

 end to form the Wiltshire Avon. The Avon here enters a chalk 

 gorge, traverses the whole breadth of Salisbury Plains in a direct 

 line, through a series of little valleys which could only have ori- 

 ginated in a transverse fissure, passes by Salisbury, enters the 

 tertiary country, and then runs direct to Christchurch. This 

 line of drainage is beautifully laid down in Mr. Greenough's map. 



Coming nearer home, the most perfect example of drainage by 

 transverse fissure, in a direct line through all the tough and 

 stony strata of the Weald, is afforded by the Arun. This river 

 takes its rise by two sources, one on each side of Horsham Forest. 

 These unite about a mile west of the town of Horsham, and the 

 united stream takes its course westward along the very centre of 

 the axis of the Weald till it reaches Rudgwick. It then turns 

 suddenly southward and runs in a direct line to Arundel Haven, 

 traversing transversely, as before said, all the courses of the 

 Wealden, the greensand, and the chalk, in a course of twenty 

 miles. 



Removal of Materials. 



The Royal Society is said to be now engaged in an inquiry 

 into the force and motive power of earthquake-waves. Till wc 

 derive more certain information from that source, we must be 

 content with some proximate data of the power of aqueous cur- 

 rents over solid materials afforded by the information occasionally 

 drifted in from various sources ; — such as the great debacle of the 

 Drance which occurred a few years ago, the Moray floods, the 

 earthquake-waves of the coast of Chili, of Scilla in Calabria, and 



* We may suppose that Mr. Hopkins meant the hne of demarcation 

 only as the boundaiv of the countiT he had himself exjdored. 



