112 



ME. J. PARKIN^SOJJT ON THE PYEOMERIDES [Feb. I 898, 



Fig:. 2. 



the boundaries of the latter, do not indicate the presence of two 

 materials of different constitution, but rather the differentiation 

 of one. 



The following figures are diagrams from Conway Mountain which 

 recall the characteristics of the Boulay Bay rocks. 



In fig. 2 the relation to flow-structure is evident enough. In 

 fig. 3 the weathered surface of the 

 matrix is rough to the touch and 

 eye ; the surface of the nodules, 

 on the other hand, is smooth ; 

 they appear more flinty and more 

 compact. In a few cases the 

 pyromerides were distinctly mam- 

 millated. Thin sections of both 

 matrix and pyroraeride have been 

 cut ; the differences are sufficiently 

 interesting to merit a short de- 

 scription. 



The matrix is characterized by 

 minute circular clear spaces, out- 

 lined by flakes and fibres of a greenish chl critic mineral. Between 

 crossed nicols these are seen to be spherulitic, with the charac- 

 teristic black cross ; the greenish mineral is very inert. Exami- 

 nation of the slide with a lens shows what the microscope does not 



Jtt nat. size. 



Pig. 3. 



[Figs. 2 & 3 represent pyromerides from Conway Mountain, 

 affected in form by fluxional movement.] 



so easily reveal, namely, that the rock is perlitic, the cracks showing 

 as clear lines and curves ; devitrification has largely hidden this 

 structure. 



The pyromeride, which was a large one, some 5 or 6 inches in 



