294 APPENDIX. 



appears to have slipped into the river, carrying with it the mass 

 of copper, together with detached blocks of sienitic granite, trap- 

 rock, and other species common to the soil at that place. 



The copper, which is in a pure and malleable state, lies in con- 

 nection with serpentine rock, one face of which it almost com- 

 pletely overlays. It is also disseminated in masses and grains 

 throughout the substance of the rock. The surface of the metal, 

 unlike most oxidable metals which have been long exposed to 

 the atmosphere, presents a metallic brilliancy, which is probably 

 attributable to the attrition of the semi-annual floods of the river. 



The shape of the rock is very irregular; its greatest length is 

 three feet eight inches ; its greatest breadth, three feet four inches, 

 with an average thickness of twelve inches. It may, altogether, 

 contain eleven cubic feet.* It exceeds, in size, the great mass of 

 native iron found some years ago on the banks of Red Eiver, in 

 Louisiana. I have computed the weight of metallic copper in 

 the rock at twenty-two hundred pounds, which is about one-fifth 

 of the lowest estimate made of it by former visitors. Henry, 

 who visited it in 1766, estimated its weight at five tons. The 

 quantity may, however, have been much diminished since its dis- 

 covery, and the marks of chisels and axes upon it, with the dis- 

 covery of broken tools, prove that portions have been cut off and 

 carried away. Notwithstanding this reduction, it may still be 

 considered one of the largest and most remarkable bodies of na- 

 tive copper on the globe, and is, so far as known, only exceeded 

 in weight by a specimen found in a valley in Brazil, weighing 

 twenty-six hundred and sixty-six Portuguese pounds. Viewed 

 as a subject of scientific interest, it presents illustrative proofs of 

 an important character. Its connection with a rock which is 

 foreign to the immediate section of country where it lies,f indi- 

 cates a removal from its original bed; while the intimate con- 

 nection of the metal and matrix, and the complete envelopment 

 of masses of the copper by the rock, point to a common and con- 

 temporaneous origin, whether that be referable to volcanic agency 

 or water. This conclusion admits of an obvious application to 

 the beds of serpentine and other magnesian rock found in other 

 parts of the lake. 



* This copper rock now (1854) lies in the yard of the War OfBce at Washington, 

 f A locality of serpentine rock has since been discovered at Presque Isle, ou 

 Lake Superior. 



