1*72 Canadian Record of Science. 



RESIDUE. 



Both suspended and dissolved matter are included under 

 this heading ; for the water was not filtered or allowed to 

 settle previous to evaporation. Yet, notwithstanding this 

 the results show the water to have heen fairly free from 

 solid impurities. The average residue, calculated from the 

 daily determinations, was 6.55 grains per gallon, the 

 maximum being 9.3 on March 11th and the minimum 

 4.06 on January 11th. Wanklyn gives 40 grains of solids 

 per gallon as the extreme quantity permissible for a drink- 

 ing water, 1 and ours is evidently well within this limit. 



It is not necessary to dwell upon the effect on the pro- 

 portion of solid matter in running water of the country 

 through which it runs and the gases it holds in solution. 

 The river Loka, in the north of Sweden, flows over granite 

 and other hard rocks, and contains but 0.0566 grains of 

 solid matter per gallon. 2 The other extreme is seen in 

 brine wells or other mineral springs. The water furnished 

 to Montreal is partly St. Lawrence^ partly Ottawa water 

 and partakes of the nature of both. " The Ottawa drains 

 a region of crystalline rocks, and receives from these by 

 far the greater part of its waters." "The St. Lawrence 

 * . * * flows through lakes whose basins are composed 

 of palaeozoic strata which abound in limestone rich in 

 gypsum and salt. " 3 



The influence of the rock upon the water brought into 

 contact with it is well shown in the case of the spring at 

 the back of McGrill College, which, deriving its water from 

 the reservoir, has a hardness of 12.5, or about double that 

 of the water before its percolation through the walls of 

 • limestone. 



HARDNESS. 



The hardness of a water depends, as is well known, upon 

 the proportion of calcium and magnesium salts it contains, 



1 The Jordan, however, is used for drinking, although it contains 

 73 grains of solids per gallon. — Chem. Com. Life. 



2 Johnston, Chem. Common Life. 

 '■'• Hunt, Geol. Survey Report 1853. 



