MINERAL SPRINGS. 99 



below they are highly ferruginous. This is sometimes due to the difference 

 in the strata, but is also often due to the bleaching or deferruginizing power 

 of waters passing through decaying vegetation, such as leaves, roots, dead 

 trees, etc. The iron in the sand is in the form of sesquioxide, which is in- 

 soluble in pure water, but slightly soluble in water containing carbonic acid. 

 The rain water falls on the decaying vegetation of the surface, becomes 

 highly charged with carbonic acid generated by it, and percolates into the 

 underlying sand bed. Here it takes up its portion of iron, and, when it 

 finally appears again as a spring, it is highly charged with it. This, on ex- 

 posure, is again oxidized, and appears in the form of a rusty, oily looking 

 scum, often mistaken for petroleum; or as a brown slimy sediment in the 

 bottom of the spring and the stream running from it. Frequently part of 

 the oxide of iron is precipitated before the stream appears on the surface, and 

 forms layers of hard rusty scales on the top of the clay bed over which it is 

 running.* Many iron springs are also formed by the decomposition of iron 

 pyrites in the sandy and clayey strata. This mineral breaks up with the for- 

 mation of sulphate of iron and sulphuric acid, both of which are taken up in 

 the subterranean waters and appear again on the surface as ingredients of 

 chalybeate springs. The sulphuric acid sometimes attacks the clay, taking 

 up part of the alumina contained in it and forming alum. Also, it attacks 

 any lime, magnesia, potash, or soda salts that may exist in the strata, and 

 forms gypsum from the lime, epsom salts from the magnesia, and soluble 

 sulphates from the potash and soda; hence the presence of these materials in 

 many mineral springs. 



Springs such as have been described are very numerous throughout East 

 Texas. They appear in many hillsides, and especially on the bluffs of rivers, 

 coating them with a rusty scum, and often cementing the loose strata sur- 

 rounding them. 



Hynson Springs are in Harrison County, six miles southwest of Marshall. 

 Some of these are highly charged with iron, and others much less so. They 

 also contain magnesia, lime, and alkaline salts. They are situated on a hill 

 composed of sandy and clayey strata associated with iron ore, and rising 250 

 feet (barometric) above the town of Marshall. The summit commands a 

 beautiful view of the surrounding country, and from it can be seen the forest- 

 clad hills of Marion, Rusk, and Harrison counties to the north, south and 

 west. To the east the country slopes off into the dense forests of Caddo and 

 Sodo Lakes, and the Red River bottom. This property has been fitted up 

 as a health and pleasure resort by the energetic owner, Captain Hynson, and 

 promises to be one of the most popular places in the eastern part of the State. 



* Lignite beds often, doubtless, supply much carbonic acid to the surface waters. 



