284 



Cancftdicvn Record of Science. 



of this mineral. In some places these fragments of crystals 

 make up the greater part of the rock, while elsewhere they 



are very rare. The 

 larger individuals 

 can often be observ- 

 ed in the very act 

 of breaking up, in 

 which case the frag- 

 ments are but very 

 little separated from 

 one another. In a 

 microscopical inves- 

 tigation we hardly 

 find a hand-speci- 

 men of a coarse gran- 

 Fig. 4 ular variety which 



does not show to a certain degree the clastic structure, and in 

 studying a large number of hand-specimens, we can follow 

 step by step the transition from a rock which exhibits no 



cataclastic structure 

 to one which con- 

 sists almost entirely 

 of broken grains in 

 which there remain 

 scarcely any traces 

 of the original indi- 

 viduals. 



Figures 3, 4 and 

 5 are made from 

 microscopical pho- 

 tographs of sections 

 which were taken 

 Fig. c». from three different 



places in the area ; they show the progress of the granula- 

 tion as seen under the microscope. 



A very remarkable fact which was mentioned in speak- 





