124 ORYSTALINE ROCKS OF N. S. AND CGC. B.—HONEYMAN. 
Occasional bright spots with quartz polarisation occur. Other 
sections might shew more of this, as a macroscopic exami- 
nation of the rock shews amygdules of quartz, and grains in 
abundance. (b) Examined with the microscope, numerous 
black grains combine with the augite to darken the section. 
These are seen to be magnetite. Brassy crystals are also of fre- 
quent occurrence. These are of pyrite. Olivine is not observed 
in this section. The minerals in this basalt are thus labrado- 
rite, augite, quartz, magnetite, pyrite. This rock has the same 
essential minerals as the two preceding, and is a dolerite. They 
differ in proportion. It has the same accidental minerals only 
pyrite takes the place of olivine. Is the third identical with the 
first and second ? Or is it part of an older rock than these ? 
DIORITES. 
4. I take as a typical diorite a crystalline rock which 
occurs in Cape Breton, in that narrow neck of land which 
separated the waters of the Atlantic and the inland waters of 
Cape Breton but which have recently been connected by St. 
Peter’s Canal. The specimen which furnished my section is one 
of a collection made at different depths in the process of excavat- 
ing the canal, and kindly presented to the Museum by a 
gentleman residing in the locality. I visited the locality in 1861, 
after the excavation had been begun and work suspended. I then 
noticed the rock but did not examine it particularly. The 
Geological formation of the locality is Carboniferous. I collect- 
ed flora in the vicinity, the precise relation of the rock to the 
formation may be uncertain, it is likely a pre-carboniferous 
diorite. (a.) Examined with crossed nicols, it is more beautiful 
than any of the sections already described. Seven prismatic 
colours, violet, blue, orange, yellow, &c., are arranged in four 
groups and in parallel lines. This is pleochroism in the strictest 
sense. In an orange colored crystal there are 7 parallel lines. 
Turning the polariser this becomes trichroic, but without alterna- 
tion between the parallels. A very beautiful group of colors show 
the arrangement from left to right, deep blue, violet, yellow, 
orange. yellow, violet, light blue in parallel lines. Turning the 
polarizer from left to right about half a revolution the arrangement 
