140 On the Composition and Properties of Drinking- Water, 
and hence it is that hard waters are deprived of lime, or softened 
at the expense of soap. The carbonate of lime in water decom- 
poses about ten times its weight of soap in washing, and other 
salts of lime act injuriously upon soap in proportion to the lime 
they contain. Carbonate of magnesia and other salts of mag- 
nesia act upon a solution of soap in a similar manner to lime- 
salts. 
On adding a solution of soap to hard water, white curdy pre- 
cipitates are produced, and no lather appears until the lime and 
inagnesia in the water are completely thrown down by the soap- 
solution. The production of lather by the addition of measured 
quantities of soap-solution of a known strength thus affords a 
good indication of the degree of the hardness of a water. Each 
<legree of hardness indicates 1 grain of carbonate of lime, or its 
equivalent of other soap-destroying earthy compounds, in an im- 
perial gallon of water. 
The quality of the water-supply as regards hardness varies 
greatly in different towns, as will be seen bj the following 
Tables : — 
Cities and Towns supplied icith Water of a Hardness over 10 degrees. 
HarJness 
of Water, 
o 
Banbury IC • 9 
Bedford 24-3 
Birmingham 15 "5 
Bristol 17-1 
Canterbury 18 '0 
Cheltenham 12-0 
Consleton 1 T <J 
Croydon 16-4 
Deal 18-4 
Derby 14*4 
Dover 17* 
Guildford 18-5 
Leamington 18 • 5 
Hardness 
of Water. 
o 
Lincoln 11' 
London 15 " 5 
Newcastle and Gateshead .. 19 '5 
Norwich 14 "5 
Rugby 11-1 
Ituucorn 17"7 
South port iy'5 
Sunderland and South Shields 12 ■ C 
Wakefield 16" 
Warrington 12 '7 
Worthing 17-3 
York 14-3 
Hardness of Water-supply from G to 10 degrees. 
Hunliiefs 
of Water, 
o 
Accrington (5 -9 
Ashton-under-Lync .. .. !C9 
Birkenhead 8-3 
Carlisle G • 1 
Durham 7*5 
Edinburgli 7* 
Leeds 7'5 
Leicester !)-4 
Leith 7" 
Hardness 
of Water. 
9-(! 
5-9 
7-'> 
Liverpool and West Derby 
^lacclesfield 5 
Northampton 7 
North wich 9-8 
Preston G • 3 
St. Helens 8-9 
Wigan 8' 
Worcester 10 ' 
4 
