HIS TORT of the SO CI Err. xj 



neus to the little boat-harbour, called Port-in-too, near which 

 the filiceous bafalt difappears. Over this ftretch, notwitliftand- 

 ing the frequent change in the arrangement of the flrata, the 

 thicknefs of each ftratum, of both fpecies, remains pretty nearly 

 the fame, and the pofition of them all fteadily fo, viz. with a con- 

 fiderable dip to E. N. E. 



The weft fide of the peninfula, though only about 400 yards 

 diftant, confifts entirely of coarfe bafalt. It flaows a bolder face, 

 and is formed of rude maffive pillars from 60 to 80 feet long. 



" I AM aware," fays Dr Richardson, " that feveral mineralo- 

 gifts deny the fhell-bearing ftone to be bafalt, while others con- 

 tend ftrenuoufly that it is. I will not venture to decide on the 

 queftion, but muft remark, that I have never met with it but con- 

 tiguous to bafalt, and fo folidly united to this laft, that the con- 

 tinuity of the whole mafs was uninterrupted. The grain of the 

 ftone graduates, as has been already remarked, into that of the 

 common bafaltes j and the arrangement of it, and that of the ba- 

 falt, with which it is fo much mixed at Portrufli and the Skerry 

 iflands, is exadlly the fame ; the ftrata of each fcarcely differing 

 in thicknefs, and not at all in inclination. The ftrata of both 

 kinds break into prifms, and the furfaces, where acceffible, ex- 

 hibit the appearance of caufeways, differing only in this, that in 

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

 the coarfe bafalt, the quadrangle. The fufibility of both ftones 

 is alfo nearly the fame ; the fhells in the filiceous bafalt are cal- 

 cined in the fire, and many more are then difcovered which had 

 before efcaped the eye *." 



C 2 WHINSTONE 



* Dr Richardson obferves, that fome mineralogifts deny that this folfil is ba- 

 falt. Several of the members prefent when this paper was read, fome of whom 

 had examined the ftone in its native place, were of that number. It was remark- 

 ed, that though certain portions of the ftrata of this foflil bore much refemblance 

 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, undifputed bafalt, 

 which lies between the ftrata of this ftone, does not contain any veftiges of marine 



animals ; 



