'J88 BA5ALTES. 



Rpm.irkson the ceous baCalt alone, which ftrelches along the flTore for about 

 cift'of Antrkn '^ >'^''^'^' ^"^ ^'^^" changes into a third alternation, which 

 conlinues to the liitle boat-harbour, caWed Port-in-too, near 

 which the (iliceous bafalt difappear!?. Over this flretch, not- 

 withflanding the frequent change in (he arrangement of the 

 firata, the thicknefs of each ftratura, of both fpecies, remains 

 pretty nearly the fame, and (he pofition of them all fleadily fo, 

 viz. with a confiderable dip to E. N. E. • ^ 



The weft fide of the peninfula, though only about 400 

 yards diftant, confifts entirely of coarfe bafalt. It fliows a 

 bolder face, and is formed of rude maflive pillars, from 60 to 

 SO feet long, 



" I am aware," fays Dr. Richardfon, " (hat feveral mine- 

 ralogifts deny (he (hell-bearing ftone to be bafalt, while others 

 contend ftrenuoufly that i( is. I will not venture (o decide on 

 the queftion, bat muft remark, that I have never met with it 

 hut contiguous to bafalt, and fo folidly united to this laft, that 

 the continuity of the whole niafs was uninterrupted. The 

 grain of the ftone graduates, as has been already remarked, 

 into (hat of (he common bafaltes ; and the arrangement of it 

 and that of the bafalt, wilh ivhich it is fo much mixed at 

 Portrufh and (he Skerry ifland, is exactly the fame; the firata 

 of each fcarcely differing in thicknels, and not at all in incli- 

 nation. The ftrata of both kinds break into prifi;is, and (he 

 furfaces, where acceiTible, exhibit (he appearance of caufe- 

 ways, differing only in this, that in the liliceous bafalt, the 

 pentagon is the prevalent figure, and in the coarfe bafalt, the 

 quadrangle. The fufibility of both ftones is alfo nearly (he 

 fame; the fliells in (he (llireous bafalt are calcined in the fire, 

 and many more are then difcovered which had before efcaped 

 (he eye *." 



Whinjione 



• Dr. Richardfon obferves, that feme mineralogifts deny that 

 this fotni is bafalt. Several of the members prefent when this pa- 

 per was read, Come of whom had examined the (tone in its native 

 place, were of that number. It was remarked, that though cer- 

 tain portions of the ftrata of this foffil bore much irefemblance to 

 fome fpecies of bafalt, by far the greater part of the mafs bore no 

 refemblance whatever to any. 



It was alfo ftated, that the fubftance of the coarfe-grained, un- 

 tlifpiited hafalt, which lies between the ftrata of this ftone, does not 

 contain any veftiges of marine animals ; That veins often ifTue 



from 



