POSSIBLE OKIGIN OF PSEUDO BEDDING. 185 



have these involved with the Laurentian gneiss, just as the hornblende 

 schists and mica schists are, and intercalations would be produced which 

 would, as in the case of the schists, frequently simulate interbeddiug of 

 quartzite or limestone, as the case might be, with the gneiss. The deception 

 would, of course, be intensified by subsequent further deformation of the 

 crust by pressure so as to be practically beyond detection, if the clue were 

 not followed up from a starting point where such subsequent dynamic 

 agencies have not obscured the true relationship. This, the writer is per- 

 suaded, is the explanation of many of the intimate associations of gneiss and 

 quartzite or limestone, whereby rocks really metamorphic sediments are so 

 involved and welded with rocks of plutonic irruptive origin that they have 

 been taken together as a simple sequence of deposited strata. 



In some portions of the Laui'entiau country, which the attitude of the 

 flanking rocks indicates was once arched over by an anticlinal dome of the 

 latter, there are found patches of schist lying quite flat, or nearly so, upon 

 the granite, showing, in favorable cliff sections, a brecciated or intrusive 

 contact on the under side. These remnants seem to show that the anticlinal 

 dome was flat or very lowly rounded, and that only on the flanks of the 

 Laurentian boss did the strata composing the arch plunge down at high 

 angles. 



Significance of Relationship. — Bearing in mind the essential distinctions 

 which exist between the rock formations of the Ontarian and Laurentian 

 systems, both as to their lithological character and their mode of occurrence } 

 and remembering also their relative geographical distribution, the foregoing 

 statement of the relationship which obtains between the two systems leads 

 clearly and unavoidably to this conclusion, viz., that the formations of the 

 Ontarian system at one time rested, as a volume of hard rocks, upon a 

 magma which subsequently crystallized as the Laurentian granite-gneiss ; 

 so that the present line of demarkation between the two systems must be 

 regarded as representing the trace of what was once a plane of contact 

 between the then crust and the magma upon which it floated. 



This conclusion affords us a conception of the Archean which is ideal in 

 its simplicity and which gives us the key to the raveling of the mystery in 

 which the subject has been involved. The fact that the crust, which con- 

 stitutes what we now call the Ontarian system, was crumpled while it floated 

 on the magma ; the fact that its lower portions were shattered by disturbance 

 so that the magma penetrated the fissures and enclosed detached fragments ; 

 the fact that there were currents in the magma which arranged the inclusions 

 in streams and also produced the foliation of the gneiss ; the fact of contact 

 metamorphism — all these are incidental and concomitant circumstances of 

 the great essential condition of a crust resting on a magma. 



But from the nature of the rocks of the Ontarian system it is clear that 



