WATER. 



353 



oxygen forms water ; and here we must remark that water is not a mere 

 mechanical mixture of gases, as air is. Water is the product of chemical 

 combination, and as we have before said, is really an oxide of hydrogen, and 

 therefore combustion, or electricity, must be called to our assistance before 

 we can form water, which is the result of an explosion, the mixture meeting 

 with an ignited body the aqueous vapour being expanded by heat. 



The ancients supposed water to be a simple body, but Lavoisier and 

 Cavendish demonstrated its true character. Pure water, at ordinary tempera- 

 tures, is devoid of taste and smell, and is a transparent, nearly colourless, 

 liquid. When viewed in masses it is blue, as visible in a marked degree in 

 the Rhone and Rhine, at Geneva, and Bale respectively. Its specific gravity 

 is I, and it is taken as the standard for Sp. Gravity, as hydrogen is taken 

 as the standard for Atomic Weight. The uses of water and the very impor- 

 tant part it plays in the arrangements of nature as a mechanical agent, 



Fig. 341. Blowing bubbles with hydrogen gas. 



geology can attest, and meteorology confirm. It composes the greater 

 portions of animals and plants ; without water the world would be a desert 

 a dead planet. 



We sometimes speak of " pure " spring water, but such a fluid 

 absolutely pure can scarcely be obtained ; and though we can filter water 

 there will always remain some foreign substance or substances in solution 

 It is well known that the action of water wears away and rounds off hard 

 rocks, and this power of disintegration is supplemented by its strength as ? 

 solvent, which is very great. Rain-water is purest in the country as it falls 

 from the clouds. In smoky towns it becomes sooty and dirty. It is owing 

 to the solvent properties of water, therefore, that we have such difficulty in 

 obtaining a pure supply. There is hard water and soft water. The former 



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