THEORY OF RECRYSTALLIZATION. 695 



dition was lacking. In the western part of the district, while the rocks 

 were probably not more deeply buried, the deformation was much more 

 profound, and probably because of this the temperature reached 180° C 

 or more. As a consequence the mineral particles grew to a large size. At 

 places in the eastern part of the district, where the conditions were least 

 favorable for recrystallization, the quartz granules in the jaspilite average 

 about 0.01 mm. in diameter. In the western part of the district, where the 

 conditions were most favorable, the quartz particles in the coarsest jaspilite 

 average about 1 mm. in diameter. Moreover, they show little strain. 

 These particles therefore average about a million times greater than those 

 of the eastern part of the district, and hence to form one new individual the 

 material of a million old particles was utilized. This illustration gives 

 conclusive evidence of the capacity of quartz to accommodate itself to the 

 most intense deformation by recrystallization. 



The explanation suggested by Adams" for the deformation of the quartz 

 of the leaf gneisses of the original Laurentian district is movement along 

 gliding planes, as advocated by Miigge 6 in reference to ice crystals. How- 

 ever, this explanation is inadequate to explain the phenomena above 

 described, and similar phenomena for other minerals, for two reasons: First, 

 the greater dimensions of the flat new individuals always corresponding' to the 

 secondary structures in the slates and schists, are wholly independent of the 

 orientation of the original particles, and therefore independent of their glid- 

 ing or other definite planes. If gliding had taken place, it must have occurred 

 along definite crystal planes. Second, as shown on pages 686-688, the par- 

 ticles of the metamorphosed schists are very frequently, and in the case of 

 the metamorphosed sediments commonly, much larger than the original 

 particles. In many instances the particles average so much larger that a 

 multitude of old particles are built into a single new particle. In those 

 cases where different mineral particles merge to form new particles of larger 

 size, gliding along any set of definite planes can not possibly explain the 

 process; this can be due onty to solution and deposition, or recrystallization, 

 as already explained. But it does not follow from the above that where 



"Adams, F. D., Report on the geology of a portion of the Laurentian area lying to the north of 

 the Island of Montreal: Ann. Rept. Geol. Surv. Canada for 1895, vol. 8, pt. j, 1897, p. 48. 



&Mugge, O., Ueber die Plasticitiit der Eiskrystalle: Neues Jahrbuch fur Mineralogie, etc., Jahr- 

 gang 1895, vol. 2, p. 212. 



