152 The Ocean — its Currents, Tides, Depth, 



masses of copper glance, and variegated copper sometimes in 

 the form of galena. The copper glance is both compact and 

 friable, but contains variegated copper, and the whole is co- 

 vered by quartz. Iron pyrites occur in small hexaedral crys- 

 tals upon other varieties of copper glance, and porphyriti- 

 cally imbedded in it. 



The gray copper occurring in some places contains a good 

 per-centage of silver ; but the bournonite associated with it 

 contains very little, and indeed gray copper appears to be 

 poorer in silver when accompanied by bournonite. 



It has already been remarked that bismuth glance never 

 occurs without indications of the previous existence of cop- 

 per pyrites, and the same may be the case with the as yet 

 imperfectly known bismuth, silver, and lead ores which occur 

 at Wolfach in Baden, for the most part disseminated through 

 quartz, and accompanied by copper pyrites, heavy spar, fluor 

 spar, &c. 



The Ocean — its Currents, Tides, Depth, and the Outlines of 

 its Bottom.* 

 When, a short time ago, I was conversing upon compara- 

 tive or ancient geography with a friend whose mind ranges 

 over all subjects, from the epic to the abstrusest mathemati- 

 cal problem, I was reminded by him that those who are 

 acquainted with the writings of the ancients would see with 

 admiration how often a piece of knowledge, or a thought be- 

 longing to those bygone days, emerges with an applicability 

 to our new geographical views which is truly astounding. 

 Take, says he, the Homeric view of the ocean ; it was an 

 ocean, and yet an ocean stream. It covered the immeasur- 

 able earth, and yet it ran round the boundaries of all known 

 lands. Thus, the most learned of our popular poets has also 

 spoken of the region 



" Where jealous Ocean, that old river, winds 

 His far extended arms, till with deep fall 

 Half his waste flood the large Atlantique fills." 



When the poet goes on to pour his flood into 



" Slow, unfathom'd Stygian pool," 



* From Sir R. I. Murchison's Address at the Anniversary Meeting of the 

 Koyal Geographical Society, 23d May 1853. 



