BaILey. | Mineral Waters. 23 
on this point have been made under the direction of boards of 
health, both in Europe and this country. In Massachusetts, 
for instance, a study was made of the well waters with respect 
especially to their chlorin contents, and it was found that the 
line of equal chlorin content was quite closely parallel to the 
coast-line, and as the wells were farther away from the coast 
the amount of salt in the water diminished quite regularly in 
proportion to that distance. The fine particles of salt are car- 
ried in the air, especially during storms, and the rain washes 
this salt into the soil, so that its presence may be detected in the 
well waters. At Land’s End,* in Cornwall, it was found that 
rain contained 3.59 parts of salt per 10,000 parts of water, while 
the mean proportion in England is only .022 per 10,000. 
Though we may have what may be called distilled water in 
the clouds, it is evident that by the time it has reached the earth 
this water has taken up many impurities. [For instance, J. 
Pieirre estimated that in France each hectare of land received 
annually from the rain alone 78.5 kilograms of mineral matter 
which had been washed out of the atmosphere. 
The rain water, having reached the surface of the earth, be- 
gins to do chemical work on the substances which come in con- 
tact with it, and these things which the rain water has absorbed, 
especially oxygen, carbon dioxid, and organic matter, assist 
greatly in producing these chemical changes. According to 
Geikie,’ these changes may be best considered as: | 
1. Oxidation, from the oxygen in the water. Common ex- 
amples of this are the changing of the sulfids to sulfates, as the 
change which takes place in ordinary pyrite by which it be- 
comes copperas and later limonite, with the setting free of sul- 
furic acid. In all zine and lead regions, as in the southeastern 
part of Kansas, localities are found where the blend (zinc sul- 
fid) has been changed partially to zinc sulfate, and even galena 
(lead sulfid) to lead sulfate, by oxidation. 
2. Deoxidation, as when organic and vegetable maiter re- 
duces sulfates to sulfids, which, in contact with water and car- 
8. Text-book of Geology, Geikie, page 341. 
9 Text-book of Geology, Geikie, pp, 343-345. 
