1870. MACFARLANE — ON CRYSTALLINE ROCKS. 159 



last, to save my venison, I had to amuse myself by firing balls at 

 them from my rifle as they sat on and picked a fine fat quarter of 

 caribou only a few yards distant from the camp. My specimens 

 were obtained by tying a piece of meat to the pan of a rat-gin and 

 retiring a few yards from the trap : they were invariably caught 

 by the bill. The settlers, strange to say, cannot succeed in 

 keeping this bird alive in confinement. 



I did not meet with any of the Columhidoe in Newfoundland,. 

 Ectopistes migratoria, Linn., may prove an occasional straggler 



there. 



(To he continued.) 



ON THE ORIGIN AND CLASSIFICATION OF 

 ORIGINAL OR CRYSTALLINE ROCKS. 



By Thomas Macfarlame. 



{Continued from March Nuniber.) 



III. — TEXTURE OF ORIGINAL ROCKS. 



In adverting to the origin of rocks, those which have been 

 called original were described as analogous in nature to furnace 

 scoriae. This may seem a forced comparison, and it may be 

 supposed that crystalline rocks are not likely to be influenced by 

 heat ; but the truth is that nearly every one of them have been 

 shewn, experimentally, by Hall, Bischof, Delesse, and Sorby, to 

 be fusible, and to be reduced by a high temperature to the same 

 condition as furnace scoriae. But while the latter generally 

 exhibit, on cooling, a homogeneous mass, original or compound 

 crystalline rocks are most frequently seen to be composed of 

 various and difi"erent minerals. While the furnace slao-s, in 

 rapid cooling, had no time during which their chemical con- 

 stitutents could arrange themselves into difi'erent compounds, the 

 greater number of original rocks, having solidified in enormous 

 masses, and, doubtless, during long periods of time, their con- 

 stituents had opportunity for arranging themselves in such a 

 manner as their chemical affinities suggested. The minerals, 

 which were the result of this re-arrangement of the chemical 

 elements, are not, however, always readily recognized in rocks. 

 The latter have in some rare cases solidified so hurriedly that 



