GRANULATION. 675 



and 1,000,000,000 particles, respectively. One of the best illustrations of 

 mechanical granulation is that of the anorthosite described by Adams." 

 Mr. S. H. Ball has compared the size of the grains of the original anorthosite 

 and the granulated anorthosite in two specimens furnished by Dr. Adams, 

 and found that, on the average, one feldspar grain of the original rock is 

 broken into 70,000 grains. 



By granulation the volume is sure to be somewhat increased, for it is 

 not possible that the broken particles of a grain shall fit so closely as the}?" 

 did when all were parts of one crystallographic unit. The subcapillary 

 openings between the particles may be very small, but they are not so 

 minute as to be ignored. Also, not infrequently small capillary openings 

 form between the granules, and these considerably increase the volume. 



Miigge 6 has shown that ice crystals may be mechanically deformed 

 by differential movement along gliding planes without the destruction of 

 the crystals. Adams and Nicolson" have shown by experiment that the 

 same process may occur in calcite crystals: and they thus largely explain 

 the deformation of many of the marbles. This process is essentiallv 

 mechanical strain beyond the elastic limit. In so far as gliding takes 

 place, deformation may occur without diminution in size of the mineral 

 particles, and hence it contrasts very strongly with granulation. It is 

 notable that in the experimental deformation of marble by gliding, the 

 mineral composing the rock is one in which there are numerous gliding 

 planes, and how important this process may be" in reference to other 

 minerals is more or less conjectural. Doubtless it is of some consequence 

 in such minerals as have good gliding planes — for instance, the micas; but 

 probably it is of little consequence with the greater number of the rock- 

 making minerals, such as quartz, feldspar, the pyroxenes, and amphiboles. 



CHEMICAL WORK. 



- The chemical work of the zone of anamorphism, like that of the belt 

 of cementation, must be considered from two points of view — the chemical 

 changes and the resultant processes. 



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

 the Island of Montreal: Ann. Kept. Geol. Surv. Canada, new ser., vol. 8, 1896, pt. j, pp. 31-85. 



&Miigge, O., TJeber die Plasticitiit der Eiskrystalle: Neues Jahrbuch fiir Mineralogie, etc., Jahr- 

 gang, 1895, vol. 2, pp. 211-228. 



c Adams, F. D. , and Nicolson, J. T. , An experimental investigation into the flow of marble : Philos. 

 Trans. Royal Soc. London, series a., vol. 195, 1901, pp. 363-401. 



