OF PRE-CAMBRIAN ROCKS 201 
The committee then went north to the village of Bannockburn, 
about a mile to the southwest of which, on the road, they found a 
great body of massive diorite or amphibolite in contact with the same 
limestone series, the two rocks being folded together along their 
contact. The appearance of this dioritic mass near Bannockburn 
suggests somewhat, in the traces of ellipsoidal structure which it 
presents, certain Keewatin rocks of the Lake Superior region. 
The committee then visited the district about Millbridge on the 
Hastings road, where they again found the same limestone series 
which here, being very free from igneous intrusions, is comparatively 
unaltered in character and preserves its original blue color. This 
body of limestone, however, although apparently uniform in char- 
acter, is seen, on a careful study, especially of the weathered surface 
to contain many thin, interstratified layers which are much harder 
than the limestone itself, and which when examined under the 
microscope are found to be composed almost entirely of silicates, 
chiefly feldspars, both plagioclase and orthoclase, with quartz and 
some biotite. ‘The rock composing these layers now shows a perfect 
“‘pflaster’? or pavement structure, and is completely crystalline. 
It is, however, of undoubtedly sedimentary origin and has been 
referred to by Adams as “‘paragneiss”. ‘These bands are of import- 
ance as representing in this comparatively unaltered portion of the 
limestone formation rocks which, when the alteration of the formation 
is more pronounced, assume a much more distinctive form. 
From Millbridge the committee went north on the Hastings road, 
which, running at right angles to the strike of the rocks, affords a 
most admirable section through the sedimentary series with its various 
interstratified rocks, for a distance of thirty miles north of Millbridge, 
where the sedimentary series becomes torn to pieces by the great 
invasions of the granite bathyliths to be mentioned later. 
About three miles to the north of Millbridge a great intrusion of 
more or less altered gabbro, about two miles in width, was crossed. 
This was found to be nearly massive in character and to alter the 
intruded sedimentary rocks. 
Crossing over this intrusion, the limestone series was again encount- 
ered, the Hastings road for the next six miles passing over more 
or less continuous exposures of limestone, interstratified in places 
