Mineralogy and Geology of Nova Scotia. 297 
sents every where a uniform geological character; and containing 
fossil organic remains, belonging to the marine world alone, and 
some of them of the oldest kind, it must obviously, according to 
the common geological division, be regarded as transition rock,* 
and as having existed long before the neighbouring Plutonic rocks 
had emerged from the central regions of the earth. That this 
rock is older than the trap rocks we have additional evidence, 
derived from another source, which we shall state by and by, 
when our observations are directed more particularly to the iron- 
ore bed, which we have no hesitation in saying extends throuhg 
the whole clay slate formation. That itis newer than the granite 
will appear evident from reasons to be assigned. 
The direction of the strata composing this formation is uni- 
formly north, 60° east, dipping at an angle of 50° or 60° from 
the horizon. The color of the rock, on fracture, is black, greyish, 
or bluish-black. Its structure is slaty or foliated, frequently sepa- 
rating by a gentle blow into broad sheets, which are sufficiently 
smooth and compact to be employed for writing-slate. This is 
the case at Rawdon, where it is obtained for this purpose, and also 
extensively quarried for roofing-slate. In other places being less 
distinctly foliated, its tendency is to break into huge rhomboidal 
fragments, as it has natural seams both in the direction of, and at 
right angles with its stratification. This renders it a valuable 
building material as it forms convenient shapes for rearing walls 
of houses, for which purpose it is employed in many places. 
The soil resulting from, and lying over this formation, is much 
inferior to that produced by the disintegration of the trap rocks 
"The term transition, although objectionable in some respects, we have adopted 
for the want of a better; it certainly conveys what is very apparent, the interme- 
diate character of the rock, to which it is applied in this paper. 
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