06. Geological Survey of Canada. 



stant, although in smaller quantity, equally belongs to the soluble con- 

 stituents of the water. The quantity of silica annually carried to the sea 

 in solution by the St. Lawrence and similar rivers, is very great, ana 

 doubtless plays an important part in the silicification of organic remains, ' 

 and in the formation of silicious deposits, both directly and through the 

 intervention of silicious infusorial animals. 



As regards the question of a supply of water f jr the city of Montreal, 

 it is to be remarked that the composition of these waters will be sub- 

 ject to considerable changes with the different seasons. The waters from 

 the melting of the snows and autumual rains, will give to the river a 

 character somewhat different from that presented after the long droughts 

 of summer, or after several months of continued frost, when we may 

 suppose that the water will contain the largest amount of soluble 

 matters. 



The waters of the St. Lawrence meeting those of the Ottawa below 

 Vaudreuil, the two' flow side by side, and may, as is well known, be dis- 

 tinguished by their difference in color. The clear greenish-blue of the 

 larger river contrasts strongly with the amber-brown color of its tribu- 

 tary. The agitation of the current however gradually mingles the two 

 streams ; and even the brown water along the front of the island of 

 Montreal is already mixed with a considerable portion of the St. Lawrence 

 water, as will be evident from the analyses given below. As but a portion 

 of the Ottawa enters the channel of the St. Lawrence at the head of the 

 island, and as the volume of the former river is very variable it 

 happens that the proportions of the mixture at a given point in front of 

 the island are subject to considerable changes. At the close of the 

 summer and winter seasons the waters of the Ottawa are comparatively 

 low, and then it may be observed that the water supplied by the City 

 Water Works is but slightly colored, the water of the St. Lawrence pre- 

 dominating; while during the spring floods its deep color shows the larger 

 proportion of Ottawa water. It hence follows that the purity of our 

 supply of water is in an inverse ratio with its color, and that in obtaining 

 an uncolored water we exchange a small proportion of organic matter 

 for a much larger amount of calcareous salts." 



Several years ago Mr. Hunt announced the remarkable fact 

 that shells of the genus Lingula consist in great part of phos- 

 phate of lime. He has since analysed several additional species, 

 with the same results ; and also the recent L. ovalis, which was 

 found to contain 61 per cent, of earthy matter, consisting* of, — 



" Phosphate of lime 85.79 



Carbonate " ] 1 .Vo 



Magnesia '. . . 2.80 



100.34 



