1 50 The Ottawa Naturalist. [October 



which composed the sands were clearly seen to be arranged 

 in order of specific gravity, the heaviest at the bottom of 

 the series and the lightest at the top. Thus it was ascertained 

 upon examination of a small bay about 200 yards above the last 

 fall and rapids of the Gatineau at the Isl md, that the upper sand 

 consisted almost exclusively of fine rounded grains of pure quartz, 

 well sorted and tree from impurities, whilst the lowest consisted 

 of numerous grains of magnetite or other ores of iron in the 

 shape of minute cry}^tals, besides other impurities, hornblende, 

 mica, garnet. The intermediate series of sand materials was of a 

 decided gray colour, the lowest being dark in colour, whilst the 

 uppermost sands were of a light yellowish colour, and the grains 

 almost exclusively quartz.t 



In the band ot hornblendic gneiss above the falls were 

 noticed aggregations of the jet black variety of hornblende. 

 This is the rock which has often been collected from the Gatineau 

 valley and brought to Ottawa for examination as coal. It might, 

 from its brilliant black lustre and general appearance, be termed 

 the "Gatineau coal." 



Several pot holes were also observed in the harder rocks of 

 the upper portion of ths falls, but these were comparatively shal- 

 low. In the bottom of one, eleven inches deep, was a mass of 

 gravel and rusty sand five inches deep ; the largest pebble was 

 about three inches and a-half in length and two inches in its 

 greatest thickness. Many of the rock surfaces of the river bed 

 now exposed at low water were polished quite smooth by the 

 rushing waters charged with sand, gravel or similarly hard, gritty 

 and rocky detrital matter. 



Near the head of the island were seen partially di-solved 

 crystals of light pink coloured orthoclase felspar, held in a paste of 

 somewhat darker coloured pink pegmatite, which appeared as 

 rounded masses resembling plums in a pudding, and giving the 

 whole the appearance of a conglomerate. These crystals vary 

 in shape and size from a few milimetres to four centimetres in 

 diameter. The rock has also a spotted appearance. 



Among other phenomena observed and discussed on the spot, 

 in the course Of an examination of the rocks of the district about 

 Chelsea, there were noted the well-marked raised beaches and 



