Correspondence. 227 



accept, as either exculpating an officer of the Greological Sui-vey, or 

 acquitting him of following an example patently bad. 



In such instances one mis-statement becomes a precedent for 

 another, and although such precedents may fairly be brought forward 

 in extenuation, still they do not, as Mr. J. Geikie would have us 

 believe, entirely exonerate himself. 



For this purpose, he quotes names of the highest authority in othei 

 branches of geology, as Lyell, Phillips, and Dana. I would, however, 

 not do Sir Charles, our great expounder of geological principles, the 

 injustice to suppose that he would attempt to enforce strictly the rock 

 definitions contained in chapters xxviii. and xxxiii. of his Elements 

 as a standard for exact petrological comparison ; nor, do 1 imagine, 

 would the cautious Professor Phillips think it fair-play if the chapter v. 

 of his Manual was to be dissected for similar purposes ; and still less 

 would the celebrated mineralogist Dana commit himseK, without 

 reserve, to the rock definitions given in p. 246, vol. ii., of his 

 Mineralogy, where he does happen to allude to mica-slate as a gneiss 

 with a distinctly foliated structure. 



In questions of petrology, instead of quotations from works on 

 general or elementary geology, I had expected to have been referred 

 to works specially devoted to that subject ; but, with the exception 

 of the recent translation of Cotta, on the classification of rocks, a 

 work acknowledged not to fulfil the requirements of the present 

 state of science,^ Mr. James Geikie does not even allude to them.^ 



Mr. James Geikie deprecatingly expatiates on the profound know- 

 ledge of chemistry, mineralogy, etc., which he declares I would 

 require of the geologist, evidently not wishing to acknowledge that 

 the pith of my argument was but intended as a warning to those 

 geologists who really possessed no knowledge of these sciences not 

 to expose themselves to just criticism by filling their pages with 

 unwarranted or unsound chemical or other data or hypotheses. 



The geologist who enters into the details of any one department 

 of his science, will regard "Admirable Crichtons" as fossils from 

 a very early period of science, for nobody knows better the ab- 

 surdity of any man, however talented, pretending to be an authority 

 on all branches of any one science ; for in this century every science 

 presents far too wide a field for any single labourer to cultivate all 

 parts of it properly, or in other words, to be at the same time " well 

 up " in every department. 



From time to time, in geology, as in every other science, the ap- 

 pearance of a generalising mind like Lyell is required to take up the 

 accumulating chaos of facts, and mould them into shape : the true 

 steady advance of geological science depends, however, in greater 

 part upon the labours of the working bees who provide these data, 

 by (without attempting to grasp too much) devoting their energies 

 to the minute and careful investigation of some special branch, how- 



^ Vide Eeviews in Geological Magazine and Atheneum 



2 There is no want of special works on this subject ; to witness the publications of 

 Blum, Brongniart, Coquuiid, D'Halloy, Erdman, Leonhardt, Mayer, Maccullooii, 

 Piukerton, Koth, Senit, Serres, Zirkel, etc. 



