Professor Keilhau on Contact Products. 155 



Pusch remarks in regard to examples i and /, that these masses 

 of ore were originally nothing else but strata of one or the other 

 of the including masses of rock, which were metamorphosed 

 to what they now are. That this geologist, who in other re- 

 spects does not seem to oppose the prevalent geological opin- 

 ions, should have recourse to such a view, which certainly 

 would only be adopted in the greatest need, must be a 

 proof of the absence at the locality cited of all arguments 

 in favour of the volcanic hypothesis. As to the opinion 

 itself, undoubtedly it can only be approved of in part ; we 

 are certainly forced to the avowal, that the spaces which 

 are now filled with ores were formerly occupied only by a 

 mass of barren rock ; but the assertion that this mass has been 

 converted into ore, belongs to those modes of speaking which 

 set all experience at defiance, and which properly deserves 

 blame. If it be the intention by this expression only to pro- 

 hibit absolutely the natural idea, that the material for the 

 ores was conveyed from without, but by some means not yet 

 explained, then there is here an unseemly anticipation ; and 

 if it be only meant that we still know absolutely nothing 

 about the origin of such products, then the selection ought not 

 to have been made of an expression which may so easily lead 

 to misconceptions. 



It may easily be imagined what an unyielding volcanist will 

 say to examples m and n ; it is only necessary to recal Pro- 

 vost's expressions regarding the appearances in the Promon- 

 tory of Melazzo. I have brought forward these cases, be- 

 cause they afford good examples of the phenomenon observed 

 by me in Norway, and which, upon the whole, seems by no 

 means to be of rare occurrence, in which not merely modifi- 

 cations of the masses in contact have been produced, but even 

 entirely new products have been called forth, where older 

 rocky surfaces are covered by deposits of a newer period. The 

 observer who reports on the above mentioned iron-ore, and 

 who is undoubtedly a perfectly impartial witness, says, •' that 

 the ore appears as a bed lying between the primitive rocks 



of true fissure veins to the category of contact-formations, is an idea which would 

 probably be far from unproductive for the theory of veins in general. Compare 

 farther on. 



