CRYSTALINE ROCKS OF N: S. AND C. B.—HONEYMAN. 129 
The microscope shows magnetite in grains. The rock is thus 
composed of hornblende albite (?) quartz and magnetite. 
11. At the head of Yarmouth Harbor is a peculiar hornblendie 
rock. In the paper on the Geology of Digby and Yarmouth, 
this rock has been pointed out. In my other paper on Polariscopic 
examination, I have referred to some of the peculiarities of a 
section of it. I referred to part of its hornblende with a singular, 
glassy inclusion. I have now ascertained the character of the 
other chief constitutent of this rock. Comparing it with the 
section of a typical quartzite, I find it has a similiar dichroism, 
blue and yellow, only the granulation of the rock is much finer. It 
requires a higher power to distinguish it, when the polarizer is 
not used. Glassy portions which do not transmit light, with the 
crossed nicols occur in the quartz constituent of the rock as well 
as in the hornblende. (b.) The microscope shews these to be 
magnetite. The constitutents of this rock are therefore, quartz, 
hornblende, magnetite, glass with or without inclusions. The 
rock is metamorphic and of Lower Cambrian age. 
INFERENCES. 
There are several interesting points that are brought into. 
prominence by these examinations. 
Ist. The value of the Polariscope and Microscope to the 
practical geologist. This is evident from the correspondence 
between observation in the Field and the Polariscope-microscope 
and from the comparison of observations in my published papers 
with the observations just submitted. The names given to rocks 
examined in the Field are in accordance with the names which 
the Polariscope and Microscope designate, and conclusions arrived 
at there have been confirmed by the process of examination. | 
2. In every rock examined magnetite is found. It is thus 
seen to be distributed far more extensively than we could have ~ 
ascertained without the aid of the microscope. 
4. It reveals to us.the origin of some of our magnetic sands, 
é.g., magnetite was found among the gold and garnet sand at _ 
Jegogsin Point. The source of the garnets was obvious and the 
probable source of the gold was indicated. That of the magnetite 
only was uncertain. Hornblendic rocks, like these of Yarmouth 
