350 R. W. ELLS — LAURENTIAN OF THE OTTOWA DISTRICT. 



tion. Their general character is that of syenitic gneiss. Their general color is 

 reddish, and it arises from the presence of reddish feldspar, which is the prevailing 

 constituent mineral. The feldspar is, however, often white or bluish-gray. The 

 rock is in no case thai I have seen without quartz. Hornblende is seldom absenl 

 and mica very often present. The prevailing color of the quartz is white, hut it is 

 often transparent or translucent. The hornblende is usually black and sometimes 

 green. The mica is often black, frequently brown, and generally of a dark tinge- 

 The rock (carefully distinguished from dikes) is almost universally small grained. 

 and though the constituent minerals are arranged in parallel layers, no one con- 

 stituent so monopolizes any layer as to exclude the presence of others, but even in 

 their subordinate arrangement there is an observable tendency to parallelism ; a 

 thick bed of reddish feldspathic rock, for example, will, in section, present a num- 

 ber of short dashes of black hornblende or Mack mica, all drawn in one direction, 

 destitute of arrangement apparently, except in regard to their parallelism, or it 

 will be marked by parallel dotted lines, composed of these minerals. The constit- 

 uents of these lines will be interrupted irregularly, and before one ends another 

 will commence above or below it, the lines interlocking among one another. 

 Sometimes these continuous parallel black belts will run in the rock for considera- 

 ble distances or it will be barred by parallel streaks of white quartz or white 

 feldspar, in which, as well as in the red part, these dark and dotted lines will occur. 

 The same description of arrangement will be found where the whole ground of the 

 rock is white instead of red, and then the red feldspar will occasionally constitute 

 streaks. There is no end to the diversity of arrangement in which the minerals 

 and the colors will be observed, hut there is a never-failing constancy in respect to 

 their parallelism, which, however, though never absent, is sometimes obscure." 



In the Geology of Canada, 1863, page 23, it is stated that — 



" Very large masses of this rock are frequently coarse grained. These are usually 

 very feldspathic, the feldspar being in cleavable masses, often attaining an inch or 

 more in diameter, which the mica and the quartz, often accompanied by horn- 

 blende, and the former sometimes replaced by it, are distributed among the feld- 

 spar in such a manner as to give a reticulated aspect to the surface of the rock. 

 Beds of this character are sometimes thin, but when thick, which they usually 

 are, might on first inspection Lie mistaken for intrusive igneous instead of altered 

 sedimentary masses. 



"The dip of the strata is generally at high angles, hut many undulations and 

 contortions exist. Some of the former give northern : others, southern dips." 



Present View. 



• 

 It will be seen from the preceding quotations that the views then held 



as to the Laurentian rocks regarded them as almost entirely of sedimen- 

 tary origin, and that these were subsequently altered by metamorphism. 

 While it is evident from the clearly interstratified character of many of 

 the beds, such as gneiss, quartzite ami limestone, that these have been 

 produced from true sedimentary deposits in the same way as the Potsdam 

 and Calciferous <>( a later date, it has been very conclusively pointed nut 



