210 The Rev. W. Conybeare oh 



completely broken through. The ruins of an ancient tower rise above 

 this chasm, on the sides of which the course of an enormous whin 

 dyke may be traced ; and the whole promontory is shattered in 

 every direction, masses of basalt (sometimes mingled with chalky 

 debris and flints) protruding through numerous fissures. The 

 chalk, where it comes into contact with these dykes, is often con- 

 verted into a compact and crystalline marble. 



The mass of chalk just described is covered by thick beds of ba- 

 salt ; but near the top of the cliffs, which here rise about 300 feet, 

 are seen two other beds, which viewed from a small distance ap- 

 pear to be chalk, one rising to the surface above the western, and 

 the other above the eastern extremity of the inferior chalky mass. 

 These, on nearer examination, appeared to be a breccia composed of 

 fragments of chalk, of various sizes, intermixed with flints and ba- 

 saltic concretions. The outer surfaces of these fragments are much 

 altered, and they are penetrated by small nests of a greenish sub- 

 stance appearing to be steatite, the interior presenting the chalk in 

 its usual state. 



The opposite coast of the island of Rathlin exhibits, as will be 

 seen by the section of it in Plate 10. an exact analogy to that of 

 the main land ; and on that point of it lying directly over against 

 Kenbaan head, a singular combination of dykes occurs, seeming 

 to be continuations of those which at the latter place appear to 

 have been attended with such extraordinary disturbances. Here, 

 within the distance of 90 feet, three dykes may be seen traversing 

 the chalk, which is converted into a finely granular marble, where 

 contiguous to the two outer dykes, and through the whole of the 

 masses included between these and the central one : these dykes are 

 situated a little to the west of Church bay, they are marked in the sec- 

 tion Plate 10 ; and a ground plan, on a larger scale, is added in PI. 

 11. fig. 2. representing their appearance as traced upon the beach. 



