GEOLOGY OF MOOSE RIVER GOLD DISTRICT — WOODMAN. 67 



of slipping or corrugation of the sediments ; because either would 

 produce structures diagonal to the vein, giving corrugations 

 which would not be persistent in the vein for more than a few 

 inches or feet, and which would appear to start on one side of 

 the vein, pass through it obliquely, and come out on the oppo- 

 site side at a distance along the strike of the vein. This has 

 never been observed. The only explanation remaining, therefore, 

 is that the cross veins lie in fissures which had their present 

 sinuous course at the beginning of occupancy by the vein 

 material. It is noticeable that this crenulation is not found in 

 quartzite, unmixed with slate ; but is confined to slate and 

 alternations of the two. It is best developed where no quartz- 

 ite is present. It appears, then, that in the thinly laminated 

 pelites, at the time of intrusion of the cross veins, the rock broke 

 under strain most easily across the strata squarely or diagonally 

 in places, with the bed ding in others, and in some backward or 

 downward rather than upward. 



Rolls. — In the stratified leads, most of the corrugations run 

 horizontally or with a low dip. Where the anticlines plunge 

 downward, however, these corrugations, instead of following the 

 strike of the strata horizontally around the nose, take a course 

 intermediate between the dip and strike of the rocks. Thus 

 they may converge on the two sides of the nose of the fold and 

 in the direction of its plunge, but not so sharply as the strike 

 lines ; and they dip, but not so steeply as the strata, nor in 

 divergent directions like them. To such corrugations the term 

 " roll " is applicable. It should be restricted to this phase, but 

 is loosely used for large crenulations of an}^ kind in leads. The 

 true rolls are not well shown at Moose River, perhaps because of 

 the scarcity of well-defined rock belts. 



Pinching and swelling, so often mistaken for rolling, are not 

 common at Moose River. Indeed, they are less abundant in this 

 series as a whole than in other countries ; and never due, as often 

 there, to the sliding of one side of a sinuous vein upon the other, 

 or to the chemical enlargement of the vein by solution of its 

 walls. 



