144 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 17. 



nificant when compared with the whole) a uniform vertical cleavage 

 or foliation, with a north and south direction ; and that the rocks in 

 those countries, like AustraUa, part of India, Siberia, South America, 

 Central America, and California, which preserve this meridional 

 uniformity, are productive of gold, platina, silver, and precious stones 

 on the decomposed edges of the schists ; whilst those regions which 

 have been disturbed or bent from their normal position are more or 

 less productive in masses of the ordinary minerals, and are compara- 

 tively barren of the precious products. In speaking of the meridional 

 structure, Mr. Hopkins alludes to the N.E. variation of the cleavage- 

 planes in the northern hemisphere, more especially in the United 

 States and Europe ; but, nevertheless, he believes that the general 

 uniformity approximates more nearly to the true meridian than the 

 magnetic meridian does. 



The author observed also that, from his acquaintance during 

 numerous mining operations with the deep-seated rock-masses of the 

 Andes and elsewhere, he was convinced that the great base below 

 was more or less granitic strongly saturated with mineral waters, and 

 that it passed upwards by insensible gradations from a crystalline 

 heterogeneous compound to a laminated rock (as gneiss), and still 

 higher up to schists in vertical planes ; the peculiar varieties of the 

 higher rocks being dependent on the mineral character of the 

 "parent rock" below; the schistose rocks forming, in short, the 

 external terminations of the great universal crystalline base. 



Mr. E. Hopkins referred to some important remarks on parallel 

 lamination of nearly vertical rocks and on cleavage, made inde- 

 pendently by Humboldt*, M'Cullochf, Sedgwick |, and De la 

 Beche § ; and, leaving for further consideration the question as to 

 how the lamination and cleavage of rocks were brought about, he 

 concluded by recommending the study of the primary rocks, with 

 their various transitions and foliations, to the special notice of 

 geologists, as being of extreme interest, and likely to throw great 

 light on several important points in geological science. 



* " Sur le Gisement des Roches." 

 t " Geological Classification of Rocks." 



X " Remarks on the Structure of large Mineral Masses," &c., Trans. Geol. See. 

 2 ser. vol. iii. 



§ Geological Report on Cornwall and Devon. 



