1878-1879.] 355 



doubtful examples, but the Carnmoney neck is one of the best. 

 It was first recognised by Mr. Du Noyer, in 1868, to be a great 

 pipe or feeder of the volcanic flows. Other good examples of 

 volcanic necks are seen at Greenisland, near Carrickfergus, and at 

 Ballygalley head, near Larne. 



The silicious minerals found in Carnmoney " neck" comprise 

 many varieties of quartz, rock-crystal or Irish diamonds, and ame- 

 thyst. A variety of opal is found in abundance, some specimens 

 of which, on being pressed against a rapidly-revolving grindstone, 

 become filled in the interior with flashes of golden light, rendering 

 them most interesting and beautiful objects. This light seems 

 quite different from the phosphorescent glow produced on silicious 

 minerals by the application of heat. The reader stated that he had 

 not yet seen any notice of this in the works he had read on this 

 subject. Chalcedony is common in many stalactitic and mam- 

 milated forms, and in sheets and veins, varying from the 

 thickness of notepaper to upwards of one foot. It forms a 

 casing around all the other minerals, and passes into silicious 

 tuff and grey flint, resembling the flints of the chalk. Hydrophane 

 and cachalong occur very rarely, also hyalite or Muller's glass. 

 Zeolites are rare, and have been formed quite recently compared 

 with the silicious minerals ; they occur filling up the hollows in 

 quartz prisms and cavities between the chalcedony and rock- 

 crystal. Hullite occurs abundantly in the cavities of the dolerite ; 

 it is also got in large masses in the heart of the mammilated 

 chalcedony, and sometimes interlaminated with chalcedony, 

 opal, and iron pyrites. This iron pyrites is found disseminated 

 through the dolerite in great plenty; sometimes it is scattered 

 in bronze-coloured blotches over the entire surface of some 

 fissures. Chlorite and terra verte are plentiful, and are often 

 found mixed up with the Hullite, chalcedony, and iron pyrites in a 

 confused manner very difficult to account for. A bright blue film 

 is found on the surface of the dolerite. It is like the fumes from a 



