57 



If a map be made, marking distinctly with right lines 

 so much of the river courses, stream valleys as well as dry 

 valleys of the whole district as lie in lengths exceeding 

 two or three miles, it will appear with considerable distinct- 

 ness, that the valley lines tail on to each other (often 

 running, however, in opposite directions) and develop by 

 their persistency over great or small distances, lines which 

 may be called master lines, and subsidiary lines, of weak- 

 ness in varying directions. 



This method has been worked out by.Daubree* with 

 admirable effect, for parts of P'rance, and these lines of 

 weakness, joints, or fractures, serve as guides and indica- 

 tions in the search for the probable positions of abandoned 

 river courses, between escarpments and through them, 

 even after denudation has almost removed the last vestiges 

 by which once their course was marked. It will be found 

 then that there are strongly marked lines of weakness in 

 the Weald, running North and South, with subsidiary ones 

 between, together with lines of weakness or joints at 

 right angles to the last and complimentary to them. By 

 this means it may be shewn that this system of joints, and 

 the next are not confined to the Weald, but extencf far 

 beyond it. There are also numerous and well marked 

 lines of weakness taking a general direction N. E. by N. 

 and S. E. by S. There also appears to be a series of 

 lines of fracture which may be called Concentric with 

 the oval shape of the Weald, these latter may have been 

 produced by the Wealden upheaval, the two former systems 

 must have preceded it. 



The North and South fractures appear to be con- 

 nected with the same causes which produced the trans- 

 verse anticlinals, which Mr. Topley has so carefully 

 examined, especially in the district under discussion, and 

 which were first pointed out by Mr. Martin and Mr. 

 Hopkins. The East and West lines have not received the 

 attention they deserve, in consequence of their having 



* Geologic Experimentale. 



