Geology of the Lake Superior Land District. 15 
ally with the addition of hornblende, making syenitic beds, and 
in some the hornblende predominating gives the syenite a general 
green tinge. Some of the beds have the quality of a greenstone, 
others that of mica slate, and a few present the character of a 
quartz rock.”* These slates, he conjectures, attain a thickness 
of several thousand feet, and are well exposed at the mouth of the 
river Doré, about five miles from the Michipicoten river. The 
strike of the beds is very irregular and their dip highly inclined. 
The upper group rests unconformably on the preceding, and 
towards the base presents conglomerate beds of no great thickness, 
the pebbles of which consist of white quartz, red jasper, and oc- 
casionally slate, the whole enclosed in an arenaceous matrix. 
Higher up are found layers of chert, occasionally approaching chal- 
cedony. ‘The plates are separated by thin calcareous seams, pre- 
senting a ribbon-like appearance. 
_ In the vicinity of the disturbed parts, the chert sometimes passes 
into chalcedony and agate, and small cracks are filled with 
anthracite, which is also found forming the centre of minute 
globules, enclosed in a silicious matrix. 
Higher up in the series, the argillaceous slates become inter- 
of a purely sedimentary rock ; but the evidences of metamorphism 
are more striking as we approach the lines of igneous outburst. 
* Report of Progress, 1846-17, p. 10. + Ibid. pp. 13-14. 
