290 BASALTES. 



Rcmavkson thfebut are generally finer. At Portrufli is a large vein, and neaf 



biifakes of the jj ^ fmalier vein, not an inch thick, which, proceeding from 

 ttwU or Anrnm. ' » ' r o 



below, terminates in the (olid rock before it reaches the fur- 

 face. 



MifceUaneons Obfervaiions. 



Some of the fpecimens in Dr. Richardfon's catalogue are 

 from a quarry in a mafs of bafaitat Ballylugan, two miles fouth 

 of Porlrufli. This bafalt contains fmall cavities in its interior; 

 many of them full of frelh water, which guflies out when the 

 ftone is broken by the hammer, as if it had been in a ftate of 

 compreffion. The ftone is fo hard, and flies fo in pieces, that 

 Dr. Richardfon has not been able to colled any of the Water 

 ior the purpofe of analyfis. 



The face of the quarry in which this variety of the bafalt is 

 found is aboiit 15 feet high, and is cut into a ftralum, the 

 thicknefs of which is not yet afcerrained. The rock is entirely 

 columnar, the pillars fomewhat fmaller than thofe of the 

 Giant^s Caufeway, lefs perfect, not articulated, fometimes 

 bent, and varioufly inclined. The fides and the interior of 

 the pillars are full of cavities. In confequence of the obfer- 

 vaiions of Dr. Hamilton and Mr. Whilehurft refpecting the 

 porous texture of the air or bladder holes of the bafalles of the 

 Caufeway and its vicinity. Dr. Richardfon has examined a 

 great variety; but in no inftance, except this of Ballylugan, 

 has he found cavities, in the interior of the bafaltic rocks on 

 this coaft, though they are frequent on the furface expofed to 

 the air. 



The iaft variety of whinftone enumerated by Dr. Richard- 

 fon is the Ochrous, which makes, as he (ays, a confpicuous 

 figure in the ftupenduous precipices along the coaft of Antrim. 

 It is difpofed in extenfive ftrata of every thicknefs, from an 

 inch to twenty-four (net, and varies in colour, from a bright 

 minium to a dull ferruginous brown. 



Three remarks are made by Dr. Richardfon, that are un- 

 doubtedly of importance, and ftiow that this ftone is merely 

 bafalt in a certain Hate of decompofition. 



1 . The ochrous (Irala are extenfive ; ihey remain always pa- 

 rallel to the bafalt (Irata which they feparale ; they unite to the 

 bafalt without interrupting its folidity ; the change from the 



