AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 11 



of this theory ; and until it can be satisfactorily explained away, to attempt to 

 account for the origin of the copper by reference to the principle in question, is 

 surely, to say the least, a mere waste of words. A few other objections to this 

 electro-chemical hypothesis may be briefly touched upon. 



This hypothesis exacts necessarily a solution of the copper in some form or 

 another. Now, some of the minerals associated with these copper deposits — 

 carbonate of lime, for instance, — are readily altered by immersion in cupreous 

 solutions ; whereas the crystals of carbonate of lime actually occurring with the 

 copper, as well as those met with in its immediate neighbourhood, exhibit no 

 appearance of alteration, but retain, on the contrary, their white color and original 

 surface condition. By placing these same crystals for a short time in a solution of 

 sulphate of copper, they become converted at the surface into malachite, or into a 

 copper carbonate of similar aspect, more especially if the solution be kept at a 

 moderately elevated temperature.f Again, if the enormous deposits of Lake 

 Superior originated in this manner, might we not reasonably look for the presence 

 of vast secondary products, the results of the chemical decompositions which must 

 necessarily have taken place. It is asking almost too much to assume that these 

 secondary products may, from their solubility, or from other causes, have entirely 

 disappeared, without leaving behind them very manifest traces of their former 

 presence. But, yet again, if we assume this origin for the copper, we must 

 necessarily assume also that the cupreous solution came from above : that is to 

 say, from an overlying, not from an underlying source ; as otherwise, from the fil- 

 ling up of the fissures, the supply would quickly have been ctlt off. This involves 

 manifold difficulties of an easily imagined character. 



My object, in the present note, is not to propose theories in explanation of the 

 origin of these copper deposits, but simply to shew that if one of the hypotheses 

 already advanced with this view — that which attributes the larger copper masses 

 (in intimate association with the trap) to direct igneous action; and thesmaller, 

 arborescent an i more distinct masses to gaseous emanations as previously explain- 

 ed — be not free from difficulty ; the other, or so-cdUed electro-chemical theory, is, 

 in the cases referred to, absolutely untenable; and, amongst other reasons, chiefly 

 for this, namely : that the deposition of the copper on non-conducting bodies is 

 opposed to all known principles. It is to be hoped, therefore, that those who still 

 feel inclined to adopt and maintain this theory of convenience, will not forget to 

 enlighten us as to the cause of the peculiar departure from known laws exemplified 

 in the cases under review. 



THODGHTS ON SPECIES. BT JAMES D. DANA. 



While direct investigation of individual objects in nature is the true method of 

 ascertaining the laws and limits of species, we have another source of suggestion 

 and authority in the comprehensive principles that pervade the universe. The 

 source of doubt in this synthetic mode of reaching truth consists in our imperfect 

 appreciation of universal law. But science has already searched deeply enough 

 into the different departments of nature to harmonize many of the thoughts that 

 are coming in from her wide limits ; and it is well, as we go on in research, to com- 

 pare the results of observations with these utterings of her universality, 



* Specimens of Carbonate of Lime coloured and altered by (his process were exhibited 

 to the Section, 



