GEOLOGY OF THE NORTH WEST OF LAKE SUPERIOR. 223 



Kamanistiquia Rivers on one side, and the Pigeon River on the other — 

 for 50 or 75 miles inland. Near the Current River, the chloritic 

 slates of the eastern part of that district are over-laid by black slates 

 (argillites), under and between these being several layers of chert. 

 All such were deposited in a quiet time upon the Ai-chsean granites ; 

 red Huronians. Their stratification is regular, as even as that of tho 

 North Toronto clays, and very like it. But the whole country was 

 afterwards shattered by earthquakes ; great cracks would form, as it 

 was cooling,* or being folded by differing distribution of pressure, or 

 swelled up by volcanic gases ; and through these cracks — 50 to 200 

 feet in width, and miles in length — up rushed lava streams, over 

 flovving the slates for miles around, to a depth varying with the slope 

 of the surface and the distance from the fissure. I do not know of 

 over 50 feet in depth of lava, but I have heard of 200 feet. Where this 

 lava sheet has been glaciated or otherwise worn away, the matter which 

 filled the cracks often shows above the level, like a wall — so mark 

 ediy that these features have received the local name of "rampykes." 

 I have found several of them, and hundreds of miles of country, per- 

 haps thousands, have been deluged with lava through their agency, 

 but I have found no volcanic pipes — round or nearly so— cores of old 

 burning mountains. The Michigan geologists have remarked several 

 intercalated lava beds ; also ash beds. The fact that these are vol- 

 canic formations is so well established that there seems no I'oom left 

 for other theoi'ies : it does however appear extraordinary that from 

 the Lake of the Woods eastward to North of Lake Huron, you 

 are constantly finding this capping of diorite, evidence of the fiery 

 time, and that yet you find no round volcanic vents. 



Then follows another period ; the natural forces locally at work 

 become less imposing, and the earthquake fissures no longer emit 

 molten lava. They are, however, still occasionally formed, tearing 

 through gi'anite and chert and slate and trap, but they are from 2 to- 

 10 feet only in breadth, and appear to have become mere drains for 

 the surrounding country ; these ai-e now the i-ich silver bearing veins 

 of the Thunder Bay district — having become filled up with quartz and 

 spar, and in many cases with quantities of native silver and sulphide, 

 with zinc blende, a little galena and some iron pyrites. 



In other neighbouring regions, the trap or lava seems to have- 

 aided much in the segregation of copper. When it overflowed a latei' 



