410 The Rev. VV. D. Conybeare on M. de Beaumont's Theory 



to the age of the rothe todte, and yet anterior to that of the 

 magnesian limestone ; and still further,as we find the 90-fathom 

 dyke of Northumberland throwing down likewise the magne- 

 sian limestone, we must here have recourse to a third period of 

 convulsion. The main direction of elevation, and that which, as 

 we have seen, must be referred to the aera of which we are now 

 especially treating, ranges N. and S. Of the direction of the 

 second, we have no sufficient information : the great fault 

 exemplifying the third ranges east and west. But before we 

 can fully pronounce as to the asras of the several disturbances 

 of this great chain, this very interesting portion of our country 

 requires a much more minute investigation. It may perhaps 

 not be altogether useless, at a meeting like the present, to 

 suggest some of the objects of inquiry: 1st, according to 

 Farey, the limestone district of Derbyshire forms a vast ele- 

 vated tract, bounded on three sides, the north, west and south, 

 by a vast fault, which depresses the superincumbent shale of 

 the millstone grit formation into contact with the whole series 

 of the subjacent limestones successively, until at length along 

 the western border the lowest limestones abut against these 

 superior beds. But the existence of this fault still requires 

 more accurate examination: we do not know how far the ge- 

 neral inclination of the strata accords with this supposition. 

 Should it be found, as is not improbable, to have been assumed 

 in order to explain the position of the masses of toadstone, 

 taking these for regular and conformable beds, will it not be 

 much more probable that these intrusive rocks are absolutely 

 unconformable to the disposition of the strata on the great 

 scale, and must, therefore, afford the most fallacious evidence 

 as to the general structure of the district?* 



The fault traversing the coal-measures N. and S., nearly in 

 the line of the basset edge of the magnesian limestone which 

 Mr. Farey describes as the great zigzag fault, also stands in 

 need of corroborative evidence. 



Yet is there nothing in the existence of these faults at all 

 incompatible with what we certainly know concerning other 

 portions of this central ridge ; for proceeding into Yorkshire, 

 we certainly find where the western escarpment of the car- 

 boniferous limestone reposes on the slate beneath Ingle- 

 borough a vast fault ranging E.N.E. and W.S.W., throwing 

 down the limestone at Giggleswick Scar, &c, on the south, to 

 the same level as the slate ; and a little further south a se- 

 cond parallel fault, also a downcast to the south, causing 

 a subsidence of the coal-measures near Settle to a still lower 



[* A portion of this subject has recently been investigated by Mr. Hop- 

 kins, a notice of whose results has been given in our Number for January, 

 present vol. p. 66. — Edit.] 



