- DAWSON—LAURENTIAN GRAPHITE, 113 
may be considered settled, not only by the adhesion of the greatest 
authorities in paleontology and zoology, but by the discovery of 
similar organisms in rocks of the same age elsewhere, by specimens 
preserved in such a manner as to avoid all the objections raised to 
the mineral condition of the fossil*, and by the discovery of such 
modern analogies as that furnished by Bathybius, it may be proper 
to invite the attention of geologists more particularly to the evidence 
of vegetable life afforded by the deposits of graphite existing in the 
Laurentian. 
The graphite of the Laurentian of Canada occurs both in beds and 
in veins, and in such a manner as to show that its origin and depo- 
sition are contemporaneous with those of the containing rock. Sir 
William Logan states+ that “the deposits of plumbago generally 
occur in the limestones or in their immediate vicinity, and granular 
varieties of the rock often contain large crystalline plates of plum- 
bago. At other times this mineral is so finely disseminated as to 
give a bluish-gray colour to the limestone, and the distribution of 
bands thus coloured, seems to mark the stratification of the rock.” 
He further states :—‘‘ The plumbago is not confined to the lime- 
stones ; large crystalline scales of it are occasionally disseminated in 
pyroxene rock or pyrallolite, and sometimes in quartzite and in 
feldspathic rocks, or even in magnetic oxide of iron.” In addition 
to these bedded forms, there are also true veins in which graphite 
occurs associated with calcite, quartz, orthoclase, or pyroxene, and 
either in disseminated scales, in detached masses, or in bands or 
layers “‘ separated from each other, and from the wall rock by feld- 
Spar, pyroxene, and quartz.” Dr. Hunt also mentions the occur- 
rence of finely granular varieties, and of that peculiarly waved and 
corrugated variety simulating fossil wood, though really a mere form 
of laminated structure, which also occurs at Warrensburgh, New 
York, and at the Marinski mine in Siberia. Many of the veins are 
not true fissures, but rather constitute a net-work of shrinkage 
eracks or segregation veins traversing in countless numbers the 
containing rock, and most irregular in their dimensions, so that 
they often resemble strings of nodular masses. It has been sup- 
posed that the graphite of the veins was originally introduced. as a 
liquid hydro-carbon. Dr. Hunt, however, regards it as possible 
that it may have been in a state of aqueous solutiont; but in what- 
ever way introduced, the character of the veins indicates that in the 
ease of the greater number of them the carbonaceous material must 
have been derived from the bedded rocks traversed by these veins, 
while there can be no doubt that the graphite found in the beds has 
* I cannot, after examination of the specimen, and of others subsequently 
obtained by Sir W. E. Logan, attach any value to the supposition of Messrs. 
Rowney & King that the Tudor specimen has been produced by infiltration of 
carbonate of lime into veins, The mechanical arrangement of the lamin and 
their microscopic structure forbid such a supposition, as well as the comparison 
of them with actual caléareous veins occurring in the same rock, 
+ ‘Geology of Canada,’ 1863. 
{ ‘Report of the Geological Survey of Canada,’ 1866. 
VOL, XXVI.— PART I. I 
