842 ABOUT COMMON WATER 



twenty-three ounces of bicarbonate solution, the lime 

 will seize upon seven ounces of the fourteen, and form 

 two pounds of the nearly insoluble carbonate. In other 

 words, nine ounces of lime can precipitate thirty-two 

 ounces of chalk. Counting thus on a large scale, we 

 find that a single ton of lime, dissolved in lime-water, 

 suffices to precipitate three and a-half tons of the simple 

 carbonate. 



Let me now describe to you what I saw at Canter- 

 bury, where works for the softening of water were 

 constructed by the late Mr. Homersham, civil engineer. 

 I found there three reservoirs, each capable of contain- 

 ing one hundred and twenty thousand gallons of water. 

 There was also a fourth, smaller cistern, containing water 

 and lime in that state of fine division which is called 

 ' cream of lime.' The mixture of water and lime is 

 violently stirred up by currents of air driven through 

 it. Brought thus into intimate contact with every 

 particle, the water soon takes up all the lime it can 

 dissolve. The mixture is then allowed to stand ; the 

 solid lime falls to the bottom, and the pure lime-water 

 collects overhead. 



The softening process begins by introducing a 

 measured quantity of this lime-water into one of the 

 larger cisterns. The hard water, pumped directly from 

 the chalk, is then permitted to fill the cistern. When 

 they come together, the two clear liquids form a kind 

 of thin whitewash, which is permitted to remain quiet 

 for twelve or, still better, for twenty-four hours. The 

 carbonate of lime sinks to the bottom of the reservoir, 

 covering it as a fine white powder ; while above it is a 

 water of extreme softness and transparency, and of the 

 most delicate blue colour. This water harbours no 

 organisms. Properly conducted to our homes, no in- 

 fectious fever could ever be propagated by such water. 



