1855.] E. HOPKINS PRIMARY ROCKS. 143 



I am aware how imperfectly these remarks have been thrown 

 together, and how much still remains before the subject can be fully- 

 exhausted. I would willingly have deferred the communication 

 until the German Geologists had completed their investigations, or 

 I myself had had further opportunities of examining the country. 

 I have already stated my reasons for the course I have pursued. 

 At the same time I trust that I shall not have been altogether wrong 

 in bringing this subject before the Society, if I have directed the 

 attention of the Members to a country, the geology of which has not 

 been often discussed in these rooms, and respecting which we have 

 still much to learn. 



January 17, 1855. 

 The folio wins: communication was read : — 



'O 



On the Yertical, and Meridional Lamination of the Primary 

 Rocks. By Evan Hopkins, Esq., F.G.S. 



[Abstract.] 



The author described wide regions in several parts of the world as 

 exhibiting in their geological structure the phsenomena of successive 

 vertical bands of schistose and crystalline rocks, parallel with each 

 other, and having a meridional strike. This structural condition 

 was illustrated by several extensive and highly finished sections, 

 some of them traversing several hundred miles, made from the 

 author's own observation in Panama, South America, Australia, 

 and Ceylon. The section across the Andes*, for instance, exhibited 

 parallel bands of quartzites, porphyry, mica-schists, greenstone, 

 granite, gneiss, hornblende schists, trachyte, crystalline limestone, 

 talcose schists, and clay-slates, occurring in variable succession, with 

 a N. and S. strike, and with an almost uniform vertical dip. In 

 plains and other places where the laminated structure has not been 

 disturbed by local causes, the cleavage planes were shown to be 

 more or less vertical ; but sometimes in high ridges with precipitous 

 flanks the bands and laminae of rocks drop on both sides, from want 

 of lateral support, thus giving the appearance of a radial or fan- 

 shaped structure. 



Here and there on the edges of these laminated rocks rest hori- 

 zontal sedimentary deposits ; and it was pointed out that many of 

 these exhibited at the point of contact with the older rocks evidence 

 of their undergoing the process of vertical cleavage or lamination ; 

 the lines of stratification becoming gradually obliterated. Even com- 

 pact mud and soil lying on the edges of the schistose rocks have 

 been observed by the author to be subject (under certain conditions) 

 to cleavage and interlamination with calcareous and siliceous matter. 



Mr. E. Hopkins maintained that in all parts of the world the old 

 crystalhne or "primary" rocks exhibit (with local exceptions, insig- 



* See also Quart. Journ. Geol. Soc. vol. vi. p. 364, and PI. 31. 



