48 Mk. J. Bryce on the Discovery of Copper near Barrhead. 



the lower coal strata, where these are cut off by it. Through this 

 rock the metal is distributed irregularly in large, thin plates, usually 

 attached firmly to the rock, and also coating its surface in broad, very 

 thin films, as if laid on by the electrotype process. It occurs also some- 

 times, but more rarely, in large lumps, and in flattened dendritic masses ; 

 but no continuous lode or vein has been anywhere noticed, such as to 

 justify the establishment of mining operations, or encourage the hope 

 of a profitable working on the smallest scale. We can hardly say 

 that there is any decided indication on the surface that the metal exists 

 below. In fracturing slabs of the rock along a scarcely perceptible 

 seam, plates of the metal are often found lining both sides of the frac- 

 t\ire ; but the seam is often found without these plates. Often also 

 these ai'e found associated with a greenish-black, earthy vein, which 

 abounds in the quarry ; but this vein exists in many places whei'e there 

 is no copper. Supposing that this vein, from its peculiar aspect, and 

 the copper associated with it, miglit consist of an impure ore of copper, 

 I submitted a specimen of it to Dr. Thomas Anderson, Professor of 

 Chemistry, who most kindly examined it for me, and reports that it 

 does not contain a trace of copper, but consists merely of various earthy 

 matters. The plates, films, and lumps, are all alike perfectly pure 

 metallic copper. 



The origin of native copper has been ascribed by some to a decompo- 

 sition of its ores, and a subsequent infiltration ; and to such an origin 

 Mr. Dawson seems inclined to refer that of Cape D'Or. This would 

 assume the existence in that locality of other ores, of which there is no 

 evidence. It is a more philosophical view to regard it as an original 

 underived product. These trap rocks had their source far down in the 

 plutonic depths, in the great subterranean laboratory where all the 

 earths and metals may exist together in a state of fusion, and whence 

 the copper may have been brought up along with the earthy components 

 of the trap. The circulation of electric currents, and the development 

 of chemical afiinities throughout the mass of rock while slowly passing 

 into the solid form, would account for the deposition of the pure copper 

 in the plates and films as we now find it. Many masses of native copper 

 are found loose on the surface along the northern shores of Lake Superior, 

 the largest of which would weigh from 3,000 to 4,000 pounds. They 

 appear to be derived from great repositories of metallic copper there, 

 associated with rocks of igneous origin ; and M. Agassiz is of opinion 

 that the metal has been poured out in a melted state among the rocks 

 from a great ,/bcMs of copper, as he terms it, existing deep below the 

 surface. Such is by far the most probable origin. Trap dikes and 

 igneous outbursts are but the surface vents of the hypogene laboratories, 



