Mr. WiLiAMsoN Peile's Description of a Group of Dykes. 16 1 



fathoms (thickening however in its progress westward), runs in a nearly 

 east and west course ; and is met by two north and south Dykes, each 

 upcasting to the eastward. In the angle contained by these Dykes, we 

 find the position of the Riders, which run nearly parallel to the two 

 upcasts, and at no great distance from them. 



No. 1. 



No. 2. 



The above are two sections, or profiles, of one of the Riders (mark- 

 ed « on the plan), as shewn on the two sides of the working that had 

 crossed it, and which was about four yards wide. 



The singularity of its appearance is very striking, and it will be con- 

 ceived how varied are the forms they assume, by the difference between 

 two sections of the same Rider at so short a distance. 



The substances composing it are as follows : — a, a, a. Grey Sand- 

 stone, more or less compact, but generally, as in the large specimen. 



