4G 3IR. F. SUTTON ON A WELL AT KIRCV REDON. 
substances, sucli as salts of lime, magnesia, iron, etc. Collected as 
it generally is, it is practically free from these latter bodies ; and 
however much it may be contaminated with the impurities of the 
air, it is still “soft” water, that is to say, free from mineral impurity. 
AVhen, however, such water falls upon the earth, it sinks into it, 
and filters down through sands, gravels, and crevices, till it finds 
the level of the water already stored up in the earth. The power 
which rain water possesses of dissolving earthy substances is very 
great ; but this power is very much increased after it gets into the 
ground by the absorption of carbonic acid gas under pressure. For 
instance, pure rain, or what is the same thing, distilled water, will 
not dissolve chalk to the extent of one grain in a gallon ; but when 
charged with carbonic acid gas, such water can be made to dissolve 
as much as fifty or more grains in the gallon. Such a water will 
also dissolve the hardest flint, aird other bodies, which are only 
usually attacked by the .strongest mineral acids. This carbonic acid 
gas exists very largely in the interstices of the ground, especially 
in all the newer geological formations, and arises mainly from the 
oxidation of organic matters, such as animal and vegetable tissues, 
Avood, leaA'^es, roots, and so on ; beside which an enormous quantity 
is carried into the ground by rain water, which collects it from the 
atmosphere, in which it constantly exists to an average extent of 
four parts in every thousand. 
Of course there is less of this gas in the districts of the primary 
rocks, and the nature of these rocks is such that very little 
carbonaceous matter exists in them to form carbonic acid ; but even 
here there is some, and consequently the waters derived from such 
rocks Avill contain some dissolved mineral matters arising from them. 
In hlorfolk, as Ave knoAv, Chalk is very prevalent, not only in 
regular deposit, but also mixed up Avith gravels, sands, and clays, 
all over the county ; consequently this substance is the chief dis- 
solved mineral matter in Xorfolk Avaters ; and the quantity of it 
dissolved in springs varies from five to ten grains per gallon in 
sands and gravels,, to thirty or forty grains in the regular Chalk 
formation. Tliis Chalk, or carbonate of lime, is invariably accom-* 
panied by small quantities of magnesia, culso in the form of carbonate j 
and so constant is it, that it must be assumed as a fact that all the 
Chalk formation contains small quantities, say about three or four 
per cent, of magnesia. The Chalk also contains small quantities of 
