118 THE CANADIAN NATURALIST. [Yol. ix . 



From the above it will be seen that the water gains 3 degrees 

 in hardness on the south shore between the Lachine rapids and 

 Longueuil, while there is no great increase in mineral lime solids. 



The alkaline silicates disappear in the dried residue, and saline 

 chlorides and sulphates are increased in quantity. 



These are indications, therefore, that the water at Longueuil is 

 somewhat affected by passing the city, but not to such an extent 

 as to render the water unwholesome, although it would be much 

 safer if sand filtered. 



On the other hand, the water at Hochelaga gives considerable 

 indications of nitrogenized impurity, the result of animal decay, 

 and it is doubtful whether simple filtration would render it fit 

 for human consumption. It is evidently affected by the sewage 

 of the city both near the shore and in mid-stream. Any attempt 

 to utilize it for a water supply would be attended with great ex- 

 pense, and still involve some risk of typhoid impurities. 



WATERS OF THE NORTH DISTRICT. — 1872 and 1873. 



In contrast to the table of the waters of the St. Lawrence and 

 the south shore, the following analyses of the waters of the north 

 district will be found of interest, showing that, whilst the lake 

 waters are of remarkable purity being taken at a great elevation 

 and above the ordinary sources of impurity, the river waters of 

 the north district which drain from the Laurentides, all contain 

 alkaline silicates, and are slightly coloured with organic spores 

 giving a yellow marsh-like tinge, to the waters. These waters, 

 when conveyed for some distance in iron pipes, become of an 

 ochreous tinge, from the precipitation of the vegetable matter in 

 solution, which is unpleasing to the eye and somewhat difficult 

 of filtration. A water of similar character has been introduced 

 into Liverpool, England, and was for some time disliked on 

 account of its peculiar color ; but it has proved a wholesome 

 and useful water, and the color is no longer deepened by the iron 

 pipes which convey it from Rivington, a distance of twenty-five 

 miles. 



The waters of the north district gave the following results per 

 imperial gallon : 



