228 Correspondence. 



ever small, of the science, briiagmg in to their assistance a sound 

 knowledge (acquired by patience and labour) of so much of the 

 collateral sciences, as specially applies to the chosen department of 

 inquiry : without, however, attempting or pretending to the im- 

 possibility of being at the same time profound in such science. 



Mr. James Geikie does me injustice in making me appear to say, 

 that the development of crystalline rocks from aqueous strata '-is a 

 notion supported only by his assertion." How could I give that 

 gentleman credit for an idea far older than either of us, and cases of 

 which I have myself years ago examined and described.^ Upon 

 reference to my communication, p. 57, it will be seen that I simply 

 record a decided protest against the statement made by Mr. James 

 Geikie, when he writes — 



'■It is certain, however, that rocks, such as diallogite, hypers- 

 thenite, diorite, syenite, or even granite itself, can be developed 

 directly from aqueous rocks," etc. 



If instead of " certain," the word possible or even probable had 

 been used, I should not have objected, and now repeat that a very 

 careful inquiry into the literature of the subject, does, I consider, 

 fully warrant me in protesting against any such dogmatic and 

 sweeping assertion being made or accepted in the present state of 

 our knowledge of the subject. 



Opinions must not be represented as facts before they have 

 received general acceptance. In a question in which the geological 

 world is undoubtedly divided in opinion, no such sweeping asser- 

 tions can be admitted as evidence in investigations of such intricate 

 nature as those which are the subject of the present inquiry. 



Mr. James Geikie cites, in support of his views, the labours of 

 the late Professor Keilhau in his so-called " Transition-formation 

 of Christiania," ^ but surely, in so doing, he must be quite unaware 

 that these had long ago been most thoroughly disproved, and set 

 aside by the results of the subsequent explorations of Sir Eoderick 

 Murchison,^ and the still later researches of Professor Kjerulf,* in 

 his work upon that formation, which I would here recommend to all 

 geologists as a model for the investigation of similar metamorphic 

 phenomena as are here referred to. 



Notwithstanding my distinct statement to the contrary, Mr. James 

 Geikie seems determined to make the object of my communication 

 appear as a declaration against hydrothermal action, and will not 

 remember that it really was to examine his evidence, not to dispute 

 his conclusions ; and I now mgdntain, whatever truth may or may not 



1 Amongst others, I can refer to the highly crystalline Hornhlende rocks so ex- 

 tensively occurring on the whole of the south coast of Norway, examined hy me in 

 1853 and following year, and which it will be seen in my " Geologiske Undersogelse 

 over det raetamorphiske Territorium, ved Norges Sydkyst." Nyt Magazin for Natur- 

 videnskabeme, Vol. iv. p. 164 et seq., I have declared to be, in my opinion, all 

 formed in situ from tuffs of aqueous deposition. 



' Nyt Magazin for Naturvidenskaberne, Vol. i., 1838, and more fully in the Gaea 

 Norwegica, Vol. i., of same author. 



3 Quart. Journ. Geol. Soc, Vol. i. p. 467. 



* Das Christiania Silurbecken chemisch geognostish untersucht, 1865. 



