MINERALS AND GEOLOGY OF CANADA. 437 
series. These shew clearly the metamorphic origin of the rocks in 
question. 
Crystalline Limestone.—This rock consists of carbonate of lime in 
a semi-crystalline condition. It is usually white or pale reddish, and 
is sometimes veined or clouded with yellow, blue, green, and other 
coloured streaks and patches. Its structure is fine or coarse granular, 
somewhat resembling that of loaf sugar, whence the term “saccha- 
roidal limestone,” bestowed on this rock. Crystalline limestone 
occurs in beds amongst the metamorphic strata of the Laurentian 
and Huronian series, and also amongst those of the more modern 
series south of the St. Lawrence. The serpentine marbles of the 
Eastern Townships have already been alluded to. These limestone 
bands are not only of economic employment,—many yielding marbles 
of superior quality,—but, when occurring amongst the gneissoid 
rocks of the Laurentian series, they impart fertility to the otherwise 
too generally unproductive soil. Where the gneiss rocks are un- 
covered by Drift deposits, it is only indeed in connexion with the 
crystalline limestones or beds of feldspar-rock, that soils of any depth 
or fertility can be expected to occur. It is perhaps needless to ob- 
serve, after what has been stated in Parr II. of this Essay, that 
crystalline limestone may be distinguished from quartz and feldspar 
by being easily scratched by a knife, and also by dissolving with 
effervescence in diluted acids. For special localities of Canadian 
marbles, see Parr V. 
Crystalline Dolomite and Magnesite—In external characters and 
conditions of occurrence, the crystalline dolomites resemble the or- 
dinary crystalline limestones, but consist of carbonate of lime and 
carbonate of magnesia. A fine saccharoidal variety occurs amongst 
the Laurentian strata of Lake Mazinaw. Beds of Magnesite, con- 
sisting of carbonate of magnesia mixed more or less with feldspathic 
or quartzose matters, occur amongst the altered Silurian strata of the 
Eastern Townships. These beds are chiefly white, greenish, or 
bluish-grey in colour, and generally resemble crystalline limestone. 
Some, by weathering, become reddish-brown. (T. Sterry Hunt, 
Report for: 1856.) 
SEDIMENTARY ROCKS. 
The rocks of this division make up by far the greater portion of 
the Earth’s surface. Having been formed by the agency of water, 
