278 Mr. V. J. Martin on the Anticlinal Line of 



as they have been hitherto usually taken in practice, in comparison 

 with the length of the string, by those who have busied themselves 

 in verifying M. Foucault's law, there is no doubt, as is apparent 

 from the equations, that the accuracy of the law, and probably of the 

 period of the revolution of the apsides as dependent on the rotation 

 of the earth, may be appreciably affected. Mr. Thacker's valuable 

 and interesting contribution is confirmed by precisely identical re- 

 sults similarly worked out, and shown to us in MS. some consider- 

 able time back from the able pen of a well-known young English 

 analyst ; and, since this article has been in type, we have received a 

 communication, not essentially differing, from our esteemed corre- 

 spondent the Rev. J. A. Coombe. — Eds.] 



XLII. On the Anticlinal Line of the London and Hampshire 



Basins. By P. J. Martin, Esq., F.G.S. 



[Continued from p. 198.] 



BEFORE we quit the subject of the drainage of the Wealden 

 area, and of its connexion with the phsenomena of up- 

 heaval, it will be well to take a review of it in its totality. Much 

 has been said already of the rivers taking their courses north 

 and south through the transverse fissures, enlarged into valleys 

 by denudation. But it is of much importance for the mainte- 

 nance of the opinion we entertain of the unity of the act of up- 

 heaval, and of its suddenness, to take a comprehensive view of 

 this great feature. 



The first notice we find of it is, I believe, in Conybeare and 

 Phillips's Outlines of the Geology of England and Wales. The 

 passage is so remarkable, that I cannot refrain from introducing 

 it here. " A very interesting geological phsenomenon is presented 

 by the course of the rivers watering this district, and the arrange- 

 ment of the valleys which convey them. We have already no- 

 ticed that the two grand valleys of this district, — that of Holms- 

 dale and that of the Weald clay, — are parallel to the direction of 

 the strata ; but these do not form the channels through which any 

 of the more important streams seek the sea, for these generally 

 have their source in the central ridge of ironsand (Wealden) ; 

 and flowing thence both to the north and to the south, in direc- 

 tions nearly at right angles both to these valleys and the strata, 

 traverse the ranges of gi'eensand and chalk through gorges 

 opened across them, in their way to join the Thames on one side, 

 and the Channel on the other ; instead of being turned by their 

 escarpments into the great subjacent valleys, as they would be if 

 the fractures in those escarpments were rcpaii'ed, and forced to 

 empty themselves into Romney Marsh and Pevensey Level. In 

 no place perhaps is the important fact of a double system of val- 

 leys crossing each other transversely (a fact which we shall 



