
- . Part Il. Secr. ii. § 2.]} SOLUTION BY SPRINGS. 351 
_ Medicinal Springs, a vague term applied to mineral springs 
‘which have or are believed to have curative effects in different 
diseases. Medical men recognize various qualities, distinguished by 
the particular substance most conspicuous in each variety of water— 
as Alkaline Waters, containing lime or soda and carbonic acid, as 
those of Vichy or Saratoga; Bztter Waters, with sulphate of magnesia 
and soda—Sedlitz, Kissingen; Sali or Muriated Waters, with common 
salt as the leading mineral constituent— Wiesbaden, Cheltenham ; 
Earthy Waters, lime, either a sulphate or carbonate, being the mest 
marked ingredient—Bath, Lucca; Sulphwrous Waters, with sulphur 
as sulphuretted hydrogen and in sulphides—Aix-la-Chapelle, Harro- 
gate. Some of these medicinal springs are thermal waters. Even 
where no longer warm, the water may have acquired its peculiar medi- 
cinal characters at a great depth, and therefore under the influence of 
increased temperature and pressure. Sulphur springs are sometimes 
_ warm, but also occur abundantly cold, where the water rises through 
rocks containing decomposing sulphides and organic matter. Sul- 
phates are there first formed, which by the reducing effect of the 
organic matter are decomposed, with the resultant formation of 
sulphuretted hydrogen (p. 64). In some cases sulphuretted 
hydrogen or sulphurous acid is oxidized into sulphuric acid, which 
remains free in the water. 3 
Ou Springs.—Petroleum is sometimes brought up in drops floating 
in spring-water (St. Catherine’s near Edinburgh). In many countries 
it comes up by itself or mingled with inflammable gases. Reference 
has already (p. 173) been made to the abundance of this product in 
North America. In western Pennsylvania some oil-wells have 
yielded as much as 2000 to 3000 barrels of oil per day. That the oil, 
which is specially confined to particular layers of rock, arises from 
the alteration of organic substances embedded in the rocks of the 
erust, can hardly be doubted, but no satisfactory explanation has been 
given of the probable nature and distribution of the organisms which 
_ yielded the oil. 
. Results of the Chemical Action of Underground 
Water.—tThree remarkable results of the chemical operations of 
underground water are, lst: The internal composition and minute 
structure of rocks are altered. 2nd: Hnormous quantities of mineral 
matter are carried up to the surface, where they are partly deposited 
in visible form, and partly conveyed by brooks and rivers to the sea. 
drd: As a consequence of this transport, subterranean tunnels, 
passages, caverns, grottoes, and other cavities of many varied shapes 
and dimensions are formed. 
1. Alteration of Rocks.—The four processes of oxidation, deoxida- 
tion, solution, and hydration, described (p. 331) as carried on above 
ground by rain, are likewise in progress on a great scale underneath. 
Since the permeability of subterranean rocks permits water to find 
its way through their pores as well as along their divisional planes, 
Pir is ? Roth, op. cit. i. pp. 444, 452, 
