Origin of certain Granites, ^c. 53 



whosoever, either that the beds in question contained more or less 

 alkaline matter, or that they even contained any alkaline matter 

 whatsoever. 



In the present state of science it is an utter impossibility, by any 

 means except careful chemical analysis (not to be performed by 

 unskilled hands), to determine the presence and amount of alkali 

 contained in rocks ; and under these circumstances, geologists are 

 fairly entitled to require some explanation from the author, as to 

 whether such analysis had been made before expatiating so boldly as 

 he does, all throughout the papers, upon the alkaline nature of the 

 rocks described. 



If such analysis had been made, the simple statement of the 

 results, what alkalies had been found present, and their percentages, 

 would, in itself, have been a valuable contribution to science.^ 



In these memoirs no analyses of rocks are cited, and when such 

 expressions are found, as " they ought perhaps to be followed up by 

 analysis of the rocks," and " future chemical analysis will enable us 

 to clear up this point," it is concluded that they were not made, and, 

 in such case, statements appearing all throughout the memoir in the 

 Quart. Journ., as p. 516, "less alkaline;" p. 518, "no recognisable 

 amount of alkaline matter ; " p. 519, " greenish alkaline felspathic 

 part ; " p, 521, "portions more highly alkaline than others ; " " alkaline 

 character of strata ; " " admixture of alkaline matter ; " p. 522, 

 "highly alkaline wacke;" "harder and more compact, (in other 

 words, Zess alJcaline);"^ p. 526, " insufiBLcient supply of alkaline 

 matter;" "whenever the strata begin to get alkaline, the altered 

 crystalline areas become amygdaloidal," etc., are thoroughly unwar- 

 rantable. 



As we know that many of the hardest minerals and rocks in 

 nature contain no alkali whatever, it is difficult to imagine where the 

 author could get the notion that alkalinity was the cause of hardness- 

 in rocks, and it may be also asked, what he means, p. 526, " alterna- 

 tions of very highly basic, with less alkaline beds," as if basicity 

 was dependant only on alkaline character. 



In the same manner, the repeated statements of the presence of 

 magnesia, if not confirmed by chemical analysis, but only given upon 

 the strength of the " greenness " observed in the rocks, cannot be 

 accepted by either chemist or mineralogist.. 



Much more might be written on the chemistry of these memoirs, 

 but, to avoid extending these remarks to too great a length, only one 

 more reference will be made. 



In the communication to the Geological Magazine, p. 529, 

 Mr. James Geikie, alluding to his proofs and evidence, says, 

 " although to render them complete, they ought perhaps to be followed 

 up by analysis of the rocks." 



1 When it is remembered that a single accurate chemical analysis of such a rock, 

 which shows but a few lines in print, represents a value of from five to ten guineas in. 

 actual labour and expense to the chemist, it is easy to understand how, in general, so 

 much appears in print about the ideal composition of rocks,, and so little verification. 

 of the same by actual chemical analysis. 



' The italics are aic in memoir. 



