" CRATER NECKS" AND "VOLCANIC BOMBS." 293 



a black obsidian, and to prevent the formation of such 

 brittle material, the castings, and the moulds, which en- 

 closed 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 embedded in 

 any such matrix as now contains them. True volcanic 

 bombs and ordinary spattering lumps of lava, are, as AVC 

 know, flung 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 believe 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-Rede,' 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 sur- 

 face of the isolated rock, and this basalt rests directly upon 

 a base of conglomerate, having exactly the appearence that 



* Geologists who maybe interested in seeing the results of this 

 experiment, will fiud on the Edgbaston Vestry Hall, inEnville Road, 

 near the Five Ways, Birmingham, some columns, massive window 

 pieces, doorways, and ornamental steps cast from the fused Rowley 

 Rag and slowly cooled. 



