298 Analyses of Boohs. [April, 



sected, or traversed, by another vein, is older than the vein by 

 which it is traversed." On this principle, he proceeds, " I would 

 make a humble attempt to ascertain the relative age of the 

 veins of Cornwall." 



By a true vein, Mr. C. understands " the mineral contents of a 

 vertical, or inclined Jissnre, nearly straight, and of indefinite length 

 and depth." To the distinctive characters of contemporaneous 

 veins, he adds the following : " When these veins meet each other 

 in a cross direction, they do not exhibit the heaves, or interrup- 

 tions, of true veins, but usually unite. In a multitude of con- 

 temporaneous veins, some may appear to be heaved ; but the 

 apparent hea'/e seldom affects more than one vein, and it is, in 

 general, easy to perceive that what appear to be separate parts 

 of the same vein, are different veins which terminate at or near 

 the cross vein. When they meet with true veins, they are 

 always traversed by them. 



"With all these descriptive particulars, however, it is frequently 

 very difficult to distinguish true from contemporaneous veins ; " 

 and, for this reason, Mr. Carne arranges the veins of Cornwall 

 into three orders, of Contemporaneous, Doubtful, and True 

 veins. 



The first order comprises veins of the following substances : 

 Granite in Granite, Felspar, Mica, Shorl, Shorl-rock, Quartz, 

 Actynolite and Thallite, Axinite, Garnet-rock, Prehnite, Chlo- 

 rite, Ironstone, or lrestone (compact hornblende, with chlorite 

 and quartz), Serpentine, Greenstone, Asbestus, Agate, Calcareous 

 Spar in Limestone, Jasper, Opal, and Fluor Spar. 



The second order commences with " granite veins in slate," 

 of which the following account is given : " These have been 

 discovered in no less than fourteen places on the coast of the 

 western part of Cornwall, between Ponthleven and St. Ives 

 Head, viz. (beginning at the most eastern point). 1. About 

 half a mile eastward of Trewavas Head, in the parish of Breage. 



2. On the eastern side of Portcue Cove, in the same parish. 



3. On the western side of the same Cove. 4. At St. Michael's 

 Mount. 5. At the village of Mousehole. 6. At Rosemodris, 

 three miles south-west of Mousehole. 7. At Carnsilver, about 

 half a mile west of Rosemodris. 8. Near Whitesand Bay, 

 between the Land's End and St. Just. 9. At Porth Just, join- 

 ing Cape Cornwall in the south. 10. At Polladan Cove, joining 

 the same Cape on the north. 11. At Chycornish Carn, near 

 Botallack. 12. At Pendeen Cove, in St. Just. 13. At Polmear 

 Cove in Zennor. 14. At the Cove north of Zennor church." 



" The relative ages of those veins has been a subject of as much 

 discussion as almost any point in geology ; especially as it 

 appears to involve several other points, which are deemed, by 

 different parties, of essential consequence to their systems. I 

 believe the more they are examined, the more difficult it will be 

 found to form any consistent theory respecting them : in order, 



