322 FRAGMENTS OF SCIENCE. 



quainted with the works. At Canterbury there are three 

 reservoirs covered in and protected by a concrete roof and 

 layers of pebbles both from the summer's heat and the win- 

 ter's cold. Each reservoir contains 120,000 gallons of chalk- 

 water. Adjacent to these reservoirs are others containing 

 pure slacked lime — the so-called " cream of lime." These 

 are filled with water, the lime and water being thoroughly 

 mixed by air forced in by an engine through apertures in 

 the bottom of the reservoir. The water thus well mixed 

 with the lime soon dissolves all of this substance that it is 

 capable of dissolving. The lime is then allowed to subside 

 to the bottom, leaving a perfectly clear lime-water behind. 

 The object is now to soften the chalk- water. Into the 

 empty reservoir is introduced a certain quantity of the clear 

 lime-water, and after this about nine times the quantity of the 

 chalk-water. The transj^arency immediately disappears — 

 the mixture of the two clear liquids becomes thickly turbid. 

 The carbonate of lime is precipitated, and the precipitate is 

 permitted to subside ; it is crystalline and heavy, and there- 

 fore sinks rapidly. In about twelve hours you find a layer 

 of pure white carbonate of lime at the bottom of the reservoir, 

 with a water of extraordinary beauty and purity overhead. 

 A few days ago I pitched some halfpence into a reservoir 

 sixteen feet deep at the Chilton Hills. The sixteen feet 

 hardly perceptibly dimmed the coin. Had I cast a pin in, 

 it could, I am persuaded, have been seen at the bottom. By 

 this process of softening the water is reduced from about 

 seventeen degrees of hardness to three degrees of hardness. 

 It yields a lather immediately. Its temperature is constant 

 throughout the year. In the hottest summer it is cool, its 

 temperature being 20° above the freezing-point; and it 

 does not freeze in winter if conveyed in proper pipes. It 

 is not exposed to the contamination of either earth or air. 

 The reservoirs are covered ; a leaf cannot blow into the 

 water, no surface contamination can reach it, it passes di- 



