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characterized by its granites and allied siliceous rocks, with a soil which 

 has resulted from their weathering and destruction by glacial and other 

 agencies. The peaty character of large areas of this gathering ground 

 is evidenced in the brownish colour of the water of the river ; a colour 

 which is due not to the presence of dissolved salts, but to the products 

 of decay of vegetable matter. The results of many analyses of the 

 Ottawa River shew it to contain less than one part of solid matter for 

 te7i thousand parts of water, or less than seven grains per gallon in solu- 

 tion. At certain periods of the year it, however, contains solid matter 

 suspended in the water, causing a turbidity which you must often have 

 remarked. This is particularly characteristic of the river in spring, 

 when the swelling of the smaller streams which feed it and the fine 

 particles of clay and sand washed down from fields and roads, sufifi- 

 ciently account for its muddy appearance, while its current is rapid 

 enough to prevent the settling of this mud to the bottom. In respect 

 to suspended solid matter, however, the Ottawa River compares very 

 favourably with many others — I might say with any other river of its 

 size. The sources of the Ottawa are situated for the most part in a 

 rocky region where there is comparatively little soil to be washed into 

 its waters by spring freshets. It is quite otherwise with such rivers r.s 

 the Red River at Winnipeg, which gets its name from the highly 

 coloured ferruginous clay, which it carries in suspension ; or with the 

 Missouri and Mississippi, whose waters, joining at St. Louis, sometimes 

 contain the enormous amount of 1,225 grains of solid matter (or nearly 

 three ounces) per gallon. Vet it is from this water that St. Louis takes 

 its supply ; and it will not surprise you to learn that four settling basins 

 of large size have to be provided, so that while one is being drawn 

 from another is being filled, and the other two are settling for use in 

 their turn. Either by subsidence, as at St. Louis, or by simply cor- 

 structed filter beds, such suspended matter may be got rid of. Of 

 the principles involved in the construction of filter beds, I shall 

 speak later. 



From what has been said it will appear that absolutely pure water 

 is not to be sought for in nature. In order to prepare it we must 

 resort to the process of distillation ; and one method of carrying out 

 this process is illustrated by the apparatus before you. The water 



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