THE 



GEOLOGICAL MAGAZINE. 



No. XXXII.— FEBRXTARY, 1867. 



I. — On the Alleged Htdbothebmal Origin of Certain Granites 



AND MeTAMORPHIC EoCKS. 

 By David Forbes, F.E.S., etc. 



THE study of the crystalline and metamorpMc rocks seems liitlierto 

 to have been rather avoided by British geologists, who have 

 more exclusively devoted their attention to the stratified and fossil- 

 iferous deposits, and left this field of research all but entirely to be 

 cultivated by their continental brethren. 



Latterly, however, the subject appears to have received some 

 attention from the members of the Geological Survey of Great Britain, 

 and the present communication is devoted to remarks upon the sub- 

 stance of two papers lately published by Mr. James Geikie, of that 

 survey, respectively entitled : — 



I. — On the Metamorphic Silurian rocks of Carrick, Ayrshire. 

 Quarterly Journal of the Geological Society, vol. xxii. p. 513, et seq. 



II. — On the Metamorphic origin of certain Granitoid Rocks and 

 Granites, in the Southern Uplands of Scotland. Geological Magazine, 

 Yol. III. p. 629, et seq. ^ 



These communications, coming from the pen of one of the staff of 

 the Geological Survey of Great Britain, are sure to arrest attention, 

 and they are written in a bold, and, if without offence it might be 

 added, somewhat dogmatic style, such as would be perfectly justifiable 

 if the views therein expounded are to be regarded as representing 

 general conclusions drawn from the deliberate and careful study of 

 the numerous examples of metamorphic action which must have 

 presented themselves in the course of the Survey ; but which, if 

 considered in conjunction with several novel and rather startling 

 statements embodied in these papers, and which assuredly the author's 

 colleagues in the Survey will not endorse, may probably be considered 

 as rather " de trop." 



The publications of the Geological Survey are generally, and 

 justly regarded, as master-pieces of geological and paleontological 

 research ; and what may be termed the extra-official scientific pro- 

 ductions of the members of the Survey fully sustain the high character 

 accorded to the official publications. 



VOL. rv, — NO. xxxii. 4 



