1883. J 487 [Wadsworth. 



the micaceous scales, and from this it is probable that they are of 

 later origin than the quartz grains, and were caused by the water 

 action (hot?) which cemented the grains, altered the feldspars, 

 and transformed the sandstone into a quartzite. 1 These cavities 

 are apparently fluidal and sometimes have moving bubbles. As- 

 sociated with these are larger fluid inclusions having rapidly mov- 

 ing bubbles. These latter inclusions are generally in the quartz 

 and much resemble those seen in the quartz of granites, but they 

 are not particularly abundant and may have a similar origin to 

 those above mentioned. Indeed it would seem that if hot waters 

 bearing silica in solution should deposit that silica in the minute 

 fissures of the quartz it would produce the usual linear arrange- 

 ment of cavities and bubbles, while the deposited silica would be 

 so optically oriented that no trace of the " mending " process 

 would be visible. Microlites, trichites, zircon, magnetite, etc., 

 occur in the quartz. Some of the grains show the hair-like trichites 

 so common in the quartz of granites. Some of the quartz appears 

 to be of secondary origin, while part of the mica scales show the 

 optical characters of muscovite. 



The quartzite obtained at Red Cove is more compact, indurated, 

 and of a more uniform character than the preceeding. It also 

 contains trichites, secondary quartz, and fluid inclusions more 

 abundantly. It has a slight reddish tinge owing to the iron ox- 

 ides distributed through the section particularly in the decom- 

 posed feldspars. 



No sections were made of the schists. One coming from the 

 top of Cruib, near the center of the island, is a gray, tine-grained 

 somewhat arenaceous rock. Another from the west side of the 

 island is a bluish black argillaceous schist, almost an argillite, and 

 contains cubes of pyrite. Schist like this is common in New 

 England. 



The only specimen, in the collection of the dikes, crossing the 

 quartzites and schists is a dark gray rock with whitish and yellow- 

 ish brown spots of decomposition products, opal, etc. The sec- 

 tion is of a yellowish gray color, and under the microscope is seen 

 to be composed of divergent ledge-formed feldspars, holding be- 

 tween them irregular grains and crystals of augite, olivine, and 

 magnetite, while extending through most of the section is a dirty 

 1 A. A. Julien, American Quarterly Microscopical Journal, January, 1879. 



