INTRODUCTION. xli 



and a comparison of them with sections of the 'graphic granite/ 

 has now satisfied me that the agencies which produced the ' graphic 

 granite ' were competent to have produced the supposed Harris 

 fossil. Whether these agencies were entirely inorganic, or 

 whether the ' graphic granite ' itself may not be a metamorphic 

 form of an ancient organic structure (metamorphoses as strange 

 have undoubtedly happened), is a question which is not at 

 present to be decided by any one's ipse dixit"* \ 



Supposed Laurentian Fossil. Dr. H. A. Nicholson. Ann. & 1876. 

 Mag. Nat. Hist. ser. 4, vol. xviii. p. 75. 



A letter withdrawing the statement that the specimens noticed 

 in his former letter " were essentially calcareous in their com- 

 position/ 3 as " upon investigation, the specimens proved to be 

 composed of alternating layers of felspar and silica." The 

 writer concludes with a remark by which he identifies himself 

 with Dr. Carpenter in HIS ipse dixit : " Whether the peculiar 

 arrangement of the minerals which constitute these specimens 

 can be assigned wholly to the operation of inorganic causes or 

 not, is a question which does not in the meanwhile admit of 

 solution " ! 



We embrace the present opportunity to mention a few points 

 connected with the Harris graphic granite. Fig. 1, PL I., 

 represents a portion of the specimen presented to us by the late 

 Prof.-R. Harkness, showing lamellae of quartz and feldspar (both 

 represented vertically) ; also the striping or " striation " (charac- 

 teristic of plagioclases) intersecting the feldspar layers nearly at 

 a right angle, and taken by Dr. Carpenter for "tubular structure." 

 Fig. 3, PI. IX., represents a small portion, slightly under the 

 natural size, of a beautiful and interesting specimen (5 inches 

 by 2 inches) which has been kindly placed, with others, in our 

 hands by Dr. Heddle, the mineralogist of Scotland. The inter- 

 lamellation of the quartz (brown in the figure) and the feldspar 

 (purple) is both " strictly limited " and of " definite form." 

 The feldspar, which, from its silvery appearance, seems to be 



* The italics are ours. 



