354 



MINERALS AND GEOLOGY 



at and explored. It has been ascertained, however, that, in many 

 if not in all cases, these existing streams and rivers flowed at one 

 time in older and lower channels beneath their present beds. The 

 ancient and in general wider channels have been subsequently covered 

 up and hidden by deposits ot glacial and post-glacial age, consisting, 

 as already stated, of gravels and black magnetic sand in immediate 

 contact with the bed-rock, overlaid by clays and boulder-clays, other 

 gravels (in some places auriferous) and vegetable soil. The clays 

 and boulder-clays contain apparently no trace of gold ; and it is i.nly 

 in the lowest layer of gravel immediately above the bed-rock, and in 

 the cracks and hollows and behind projecting ridges of the bed-rock 

 itself, that gold occurs in paying quantity. All underground work- 

 ings therefore have to be carried down to the rock floor. When the 

 gravel is washed, a certain amount of black magnetic sand is almost 

 always found with the gold in the sluices, but this arises from the 

 comparative density of the sand. The black sand, in itself, is no 

 absolute indication of the presence of gold in alluvial gravels, as it 

 occurs almost everywhere in the detritus of our crystalline rocks. 



The Leda Clay and Saxicava Sand deposits (see page 342) are 

 largely displayed on the Trois Pistoles, Cacouna, Riviere du Loup 

 (Temiscouta), St. Anne, Matanne, Metis, and other rivers, at various 

 elevations from three or four, to over two hundred feet above the 

 present sea-level. 



The more superficial deposits of the district include the bog-iron 

 ores of Stanbridge, Farnham, Simpson, Ascot, Stanstead, Ireland, St. 

 Lambert, St. Vallier, Vallery, Cacouna, and ether sites ; the ochres 

 of Durham ; the shell marls of Stanstead, New Carlisle, etc.; and the 

 peat beds of the Riviere Ouelle, Riviere du Loup, Metis, Rimouski, 

 and Madawaska most of which are of great extent, and from five 

 to ten or fifteen feet in depth. 



