REVIEWS — ACADIAN" GEOLOGY. 45 



phyre, the substance of the rock consists essentially of analcime and 

 augite.* 



Briefly to sum up our review of this vexed question, it appears to 

 us that two phenomena have here mainly to be accounted for. First, 

 the connexion of the copper with trap of different ages and localities ; 

 and, secondly, its association with carbonates and hydrated minerals. 

 The former is satisfactorily met by the igneous hypothesis, but left 

 altogether unexplained by the adoption of the electro-chemical or 

 voltaic theory. The second phenomenon, if apparently opposed to 

 the igneous explanation, is, when rightly considered, equally opposed 

 to the other view. A single example, beyond the objections already 

 cited, will suffice to uphold our assertion. It is well known that the 

 Lake Superior copper frequently bears, even to the minutest striae, 

 the most distinct impressions and moulds of the accompanying cal- 

 cite crystals — shewing incontestibly that these crystals must have 

 been consolidated prior to the consolidation of the copper. Now, 

 we have found, by actual experiment, that calc-spar in aqueous 

 solutions of copper salts, is readily converted on the surface into 

 malachite : whereas, the calc-spar crystals of Lake Superior, when 

 extracted from their cupreous matrix, are perfectly white and unal- 

 tered upon the surface. Malachite, moreover, according to Whitney 

 and Foster (Second Report, p. 101), is all but unknown in the district, 

 except as a mere superficial product due to the present action of the 

 atmosphere. On taking leave of this subject, it should finally be 

 pointed out, that carbonate of lime — equally with quartz, the zeo- 

 lites, &c. — is a non-conductor : and hence in artificial precipitations 

 of copper by the process under consideration, no deposit will take 

 place upon this mineral unless its surface be coated with graphite or 

 some other conducting substance.t 



The most important rock-group of JS"ova Scotia belongs to the 

 great carboniferous epoch. The coal-bearing rocks of this system, 



* Some very interesting remarks and experiments by Professor Bnnsen of Marburg, on the 

 artificial formation of zeolitic silicates by heat, may be seen in Von Leonhard's Jahrbuch for 

 1851, p- 861. See also the Annual Address of the President of the Chemical Society of Lon- 

 don (Professor Daubeny) for 1853. 



t Two other views have also been advanced in elucidation of the origin of these copper 

 deposits. One assumes the copper to have been produced by the action of the trap on copper 

 pyrites and other ores; but this theory fails to explain the occurrence of copper sulphides 

 associated with the same erupted rock in neighbouring localities. The second theory sup- 

 poses the copper to have originated from the reducing action of free hydrogen on volatile 

 copper compounds, as Cu CI. In controversion of tins, the unparalelled amount of the cop- 

 per may be referred to. At the same time, the origin of the little vcinicts and arborescent 

 ramification-, may perhaps he rightly attributed to ' of the kind in question; but 



their deposition within znolites and other non-conducting bodies, by electro-chemioaJ ac- 

 tion on metallic solutions, is cortainly devoid as yet of any satisfactory explanation. 



