160 Mr. Williamson Peile' s Description of a Group of Dykes. 



X.YII.— Description of a Group of Dykes, termed Riders, discovered in 

 the Whitehaven Colliery. By Mr. Williamson Peile. 



Read July 20, 1830. 



The subject of the various dislocations of strata met with in collieries, 

 and included under the general name of Dykes, is one of so much in- 

 terest and importance to geologists and miners, that it is hoped no 

 apology will be needed, for laying before the Society the following 

 description of some singular Dykes, which have lately been found in 

 the workings of the Croft Pit, in this colliery. They offer too little 

 obstruction to the progress of the collier to entitle them to much of his 

 attention, but an account of them may, perhaps, be acceptable to per- 

 sons interested in the science of Geology, as adding another link to the 

 chain of facts illustrative of these most singular occurrences. 



As additional of a further interest to the subject before us, it may be 

 well to state, that similar Dykes, have never as far as I can learn, been 

 met with, in any other, than the Whitehaven Colliery. Here, also, 

 their occurrence is very rare, and always confined to the vicinity of 

 large Slip Dykes, similar to the locality we are now attending to ; in 

 which a group of them, each preserving the general features of the 

 whole, has been found. 



Plan, No. 1., Plate XIV., shews their situation, and the great confusion 

 of the district, which, will perhaps, be rendered more apparent by the 

 section No. 2, Plate XIV. The lines shaded yellow, are ordinary Slip 

 Dykes ; the red represent the Riders. 



The excavations shewn on the plan are in the Main Band, or princi- 

 pal seam of the Whitehaven district. Its depth below the surface, at 

 the place referred to, is about I7O fathoms. 



It will be seen by the plan, that a Downcast Dyke, southwards of 12 



