J20 Primllivr, Stccrii^nr^, and Dtrlvative Mcuntaini of Jfalej. 



VI. 

 Geihgical Obfervationj on North IVnIcs *. % Mr. ARTHUR AlKIN. 



1. X HERE are no proper vc'.canic proJuftions to be met with in North Wales. By 

 proper volcanic fubftanccs I mean aflies, pumice, lava, and fcorise, or femi-viirified ftones, 

 luch as are the peculiar products of Etna and other acknowledged volcanos. A variety 

 of porous (tones may be found on Cader Idris, and Snowdon ; and thcfe have been miftaken 

 for cellular lava ; they confiQ, however, merely of decompofed granite, porphyry, or toad- 

 ftone. pragmenls of this laft, indeed, I have found in the plain of Salop, fo porous, and 

 penetrated with carbonate of iron, as greatly to icfcmble a flag. 



H. The indefatigable Sauflurc, whofe accurate refcarchcs into the pofition and nature of 

 the Alps, and the other furrounding mountains, have dcfervedly ranked him among the moft 

 JUuilrious and perfevering mineralogifts, fays, in the firft volume of his Voyages dans Ics 

 Alpcs, " It is a general obfervation, with few exceptions, that, in the greater chains of moun- 

 talus, tlie exterior tidges are of lime \. the next contain flates i to thefe fucceed the primitive 

 ftratified rocks, and then the granites." The relative pofition of the Welflr mountains tends, 

 to confirm a remark made among the Swifs Alps. For if from the central ridge of llic. 

 Snowdon chain (in which tcrml comprehend the whole mountainous extent of Caernarvon- 

 fiiire from north to fouth) we proceed to the Menai, it will be found that the primitive 

 rocks in mafs, fuch as the granites and porphyries, occupy the interior and higher peaks j 

 to the fide of thefe are applied the banks of primitive ftratified rocks ; then come the flates, 

 which terminate in the lime-Ilone, which forms the bank of the Meaai. The fame grada- 

 tion of (Irata will appear, if, inftead of the weflern, we examine the eaftern fide of .Snow- 

 don ; the variation is not indeed fo fudden, but perhaps on that very account is more in- 

 terefting, as the fpecies and varieties of rocks are more numerous, and in larger mafTes. From 

 the peak of Snowdon to Llanrwft through Capel Cerig are found granite and porphyry 

 in mafs, micaceous fchlfius, and other primitive ftratified rocks; ferpentine in large blocks 

 and of extraordinary beauty, and hornblen flate mixed with veins and rocks of quartz : 

 from the vale of Llanrwft to Llangollen extend the flates, which are there circumfcribed by 

 the lime-ftone range already mentioned. The general difpofition of the mountains of North 

 Wales may be defcribed in a very few words. There are two ridges of primitive mountains 

 extending nearly due north and fouth, of which one is the Snowdon chain, and the other 

 the Cader Idris chain (comprehending, befides tliis mountain, the Arrans and other lofty 

 peaks that overlook' the fouthern extremity of B.da-rool). Owing to the near approach 

 of the primitive and fccondary mountains to the coaft of Merioneth, the lime does not com- 

 mence till near the port of Crickaeth ; hence proceeding northwards in an interrupted line 



* From " A Journal of a Tour through North Wales and Pnn of ShropOiire ; with Obrerv-ationj in Mfne- 

 ralogy ani! other Vans of Natural Hiftory." By Arthur Aikin. Small oflavo, 231 pages. Printed for Johiifon, 

 London, 1797- 



This Journal it of much value fnr the intercftlng fclcntific obrcrvations it contains, as well at frr authentic 

 accounts of the nianufaflorics and mine-works in the diftriil through which the tour w;is made. lis plan in 

 (ome rcfpcdl refcmblcs that of thc''!elcbratcd Dc SautTurCj likc^hom cur author lias given lomc animated 

 flictchcs of the grand rotiuntic fcenery of a mountain country. N. 



along 



