BY W. N. BENSON. 147 



coarse-grained dolerites occur among these. They are also greatly 

 shattered, traversed by shearing lines and long bands of crushed 

 minerals. The felspar is difficult of determination, owing to the 

 poor development of twinning, but it can never be said to have a 

 spongy structure. The pyroxene is almost entirely changed to 

 uralite. 



The Variolites and associated Dolerites. 

 These rocks form a small group quite distinct from the normal 

 spilite-dolerite series. Two occurrences may be noted as examples. 

 The first is only a single narrow dyke traversing the cherts 

 opposite Lyons' house in Swamp Creek. Variolitic texture is 

 very well shown among the felspars, while the remaining minerals 

 have become almost entirely changed to carbonates. The second 

 mass is much larger and diversified. It occurs in Munro's 

 Creek. The field-relationships have been described above. The 

 breccia-like rock on the eastern margin(1090) consists of frag- 

 ments of crystalline rock, set in a light yellow-brown glass, which 

 is hypocrystalline, in places approaching to the character of the 

 fragments which it includes. The most abundant of these inclu- 

 sions are those least different from the groundmass. They are 

 porphyritic with albite phenocrysts in a grey hyalopilitic matrix, 

 containing many laths of felspar. The proportion of glassy to 

 crystalline matter, and the extent to which flow-structure is 

 developed, differ considerably in the several fragments, as do also 

 the size and abundance of the phenocrysts. A second type of 

 inclusion is holocrystalline. It contains fewer phenocrysts than 

 the above, and has a pilotaxitic to trachytic base, consisting of 

 albite laths with a little ferromagnesian matter, chiefly epidote 

 and actinolite pseudomorphs after pyroxene. Wide variations 

 occur in the extent of development of the flow-structure and the 

 amount of ferromagnesian minerals. The type passes into the 

 one first described. In addition, there are isolated crystals of 

 albite, which project into the in^.lusions of the first-described 

 type in a manner which shows that these inclusions were still 

 plastic while they were in the glassy groundmass. There can be 

 little doubt that this is a rock produced by the consolidation of 

 a moving magma, which was shattered and the fragments were 



