8 BURTON WATERS—DRINKING AND BREWING. 
as quartz, felspar, mica, &c., which give the characteristic 
property to most of the volcanic and metamorphic rocks, 
slates, and many sandstones; and (B), those which are, 
more or less, Soluble in water, such calcite or carbonate of 
lime, gypsum or sulphate of lime, salt or chloride of 
sodium, familiar to us in the Derbyshire mountain lime- 
stone and marl beds of this district. 
The great masses of mountain limestone, chalk, and 
dolomite or magnesian limestone, have a very important 
influence upon the waters passing over and through them. 
The carbonic acid taken into solution by the rain-water in 
falling through the air, enables this water to dissolve these 
rock masses, and take into solution carbonates of lime and 
magnesia and small quantities of carbonates of iron and 
manganese. The other acids previously named as occurring 
in small quantities in rain-water, also act on these rocks, 
and pass into the ground in solution, as salts of lime or 
magnesia. 
Chlorides, sulphates and nitrates of the alkalies, sodium 
and potassium, may be taken into solution, and almost 
invariably small quantities of silica and alumina. 
Decomposing iron pyrites supplies sulphuric acid, which, 
splitting up the carbonates, yields sulphates even when 
gypsum is not found in the soil, and salt is invariably 
present in more or less quantity. 
Our spring-water may now, on the one hand, be but 
little removed from the chemically pure mixture of oxygen 
and hydrogen before mentioned, and contain but few of the 
above named bodies, or rather, but small quantities of them; 
such waters are common in rocky districts, such as Wales, 
Scotland, Cumberland, and Westmoreland, and they form 
exceptionally good drinking water supplies—hence the 
Liverpool, Manchester, Birmingham, and Glasgow water 
works at Vyrnwy, Thirlmere, Cwm Elan, and Loch 
Katrine. On the other hand, if the rock consist of lime- 
stone, or chalk, or the strata contain gypsum, the springs 
