1912] The Ottawa Naturalist. 171 



And, secondly, it was apparent that all our water supplies 

 lakes, streams, springs and wells were directly dependent 

 upon the fall of rain and snow, and therefore there was a very 

 close relationship between the annual precipitation of a district 

 and the volume of water which might be available for a water 

 supply. 



There are two properties of water that must be referred 

 to, if only briefly, in order that we may intelligently consider 

 the various classes of water that are suitable and wholesome 

 for domestic use its solvent power and its carrying power. 

 Water is known as the universal solvent. It is because of its 

 ability to dissolve gases and solid substances, whether they be 

 inorganic (mineral), or organic, and the constant exercise of 

 this power that in Nature there is no such thing as pure water 

 that is, chemically speaking. Pure water, as formed in the 

 laboratory, consists solely of oxygen and hydrogen. All natural 

 waters then, contain dissolved matter, some more, some less, 

 and, speaking broadly, the nature of this matter whether 

 injurious or harmless to health and its amount, will be deter- 

 mined by the character of the rock or soil it passes over or 

 passes through. Thus we have soft waters from the Laurentian 

 districts because the gneisses and granites are not easily soluble 

 and impart but little mineral matter to the water; and we have 

 hard waters in limestone districts, because the water with the 

 aid of the carbon dioxide it has taken from the atmosphere 

 is capable of exerting a very considerable solvent effect upon 

 such rocks and contains as a result more or less lime in solution. 

 Next to the sun, the soil is Nature's greatest water purifier, 

 for it can remove by oxidation and filtration impurities in 

 solution and suspension, but if the soil is choked with filth 

 then the water in passing through it will dissolve such and be 

 rendered foul. 



The carrying power of water is secondary to its solvent 

 power in this consideration of natural waters for drinking and 

 household purposes. The descending rain, the storms, the 

 spring freshets and floods, wash the surface of the land and carry 

 much which they find there to the nearest stream or lake. Sim- 

 ilarly the banks and channels of streams are eroded even rocks 

 may be slowly worn away and the detritus, the debris, borne 

 in the turbid waters, perhaps hundreds of miles, to be deposited 

 as their velocity is checked. In this way deltas of clay and 

 silt and fine sand mixed with organic particles are formed at 

 the mouth of great rivers, and areas of vast size and of extreme 

 fertility built up. Since turbid waters, those with clay and 

 silt in suspension, are not desirable for supplies, they must be 

 subjected to filtration. If such waters possess no organic filth, 

 the filtered and now clean water will be quite satisfactory. 



