"CRATER DECKS'' AND " VOLCANIC BOMBS." 277 



of an inner crater of Mount Vesuvius. These as they fell upon the 

 ground around me were flattened out into thin cakes. There was no 

 approach to the formation of subangular masses, like those displayed 

 upon the Dunluce cavern walls. 



Some years ago a project for melting the basaltic rock known as 

 " Kowley Bag," and casting it into moulds for architectural purposes 

 was carried out near Oldbury, and I had an opportunity of watching 

 the experiment, which was conducted on a large scale at great ex- 

 pense by Messrs. Chance. 



It was found that if the basalt cooled rapidly it became a black 

 obsidian, and to prevent the formation of such brittle material, the 

 castings, and the moulds which inclosed them, had to be kept at a 

 red heat for some days, and very gradually cooled.* 



It is physically impossible that lava ejected under water, in lumps 

 no larger than these boulders, could have the granular structure 

 which they display. 



The fundamental idea upon which this bomb theory is based will 

 not bear examination. Such bombs could not have been shot into 

 either air or water and have fallen back again into the volcanic neck 

 at any other time than during an actual eruption ; and at such time 

 they could .not have remained where they fell, and have become im- 

 bedded in any such matrix as now contains them. True volcanic 

 bombs and ordinary spattering lumps of lava are, as we know, fhmg * 

 obliquely out of active craters, and distributed around, while those 

 which are ejected perpendicularly into the air and return are re- 

 ejected, and finally pulverized into volcanic dust if this perpendicular 

 ejection and return are continued long enough. 



In the course of a rapid drive round the Antrim coast I observed 

 other examples of this peculiar conglomerate, and have reason to be- 

 lieve that it is far more common than is generally supposed. I found 

 it remarkably well displayed at a place almost as largely visited as 

 the Giant's Causeway, and where it nevertheless appears to have 

 been hitherto unnoticed viz. Carrick-a-Kede, where the public car 

 stops to afford visitors an opportunity of examining or crossing the 

 rope bridge, etc. 



Here the whole formation is displayed in a manner that strikingly 

 illustrates my theory. 



There is an overlying stream of basalt forming the surface of the 

 isolated rock, and this basalt rests directly upon a base of conglom- 

 erate, having exactly the appearance that would result from the slow 

 baking of a mass of boulder clay. 



The sea gully that separates the insular rock from the mainland 

 displays a fine section above eighty feet in thickness, and has the 

 advantage of full daylight as compared with Dunluce Cave. That this 

 is no mere neck or pipe is evident from its extent. Its position 

 below the basalt cap refutes the above quoted subsequent explana- 

 tion, which Mr. Hull and others have recently adopted. 



The heterogeneous bomb-like character of the boulders is not so 

 strongly marked as in the Dunluce rock, and this may arise from the 

 closer proximity of the basalt, which, coming here in direct contact, 



* Geologists who may be interested in seeing the results of this experiment, 

 will find on the Edgbaston Vestry Hall, in Enville Road, near the Five Ways. 

 Birmingham, some columns, massive window pieces, doorways, and ornamental 

 steps cast from the fused Rowley Rag and slowly cooled. 



