PENNSYLVANIA MINERAL SPRINGS. 125 



of immense size. These are generally common springs of 

 limestone water, or holding in solution the salts of lime. 

 There are some true mineral springs which have attracted 

 attention in this group, both in Pennsylvania and Yirginia. 



In the transition between this formation and the one be- 

 low, the waters are also frequently mineralized. In the 

 passage into the formation above, the dark slate group, 

 which contains a number of mineral elements, there have 

 been noticed some valuable waters, as also in No. 3 itself. 



In the fourth formation, (No. 4,) which we have seen, is a 

 large accumulation of silicious strata, there is but little variety 

 in the water, as the quartzose elements, constituting almost 

 the entire substance of the formation, are but slightly soluble 

 in water at the temperature of the earth The waters of this 

 formation are generally, then, soft and pure, containing few 

 mineral or organic substances in solution or suspension. 

 The next formation above, or fifth of the series, being a 

 slate group with lime, magnesian, and iron-ore strata inter- 

 mingling, the springs are consequently more diversified in 

 their character than the preceding, and belong to the 

 classes carbonated, saline, and chalybeate. The next forma- 

 tion, sixth in the ascending series, is a limestone, (No. 6,) 

 with a few interlayers of slate. Some valuable waters 

 emerge from this formation. Succeeding this is a small 

 sand group with some slate layers, too limited generally in 

 its development to give character to the waters which pass 

 through it. The next formation, olive slate, (No. 8,) of the 

 series is an enormous mass of slate or argillaceous strata 

 with silicious interminglings. There are also in the lower 

 part of the formation some calcareous layers ; also a quan- 

 tity of the carbonate and sulphuret of iron. That portion 

 of the formation containing these substances is a soft black 

 friable slate. As would be expected from the number of 

 mineral elements above enumerated, most of which possess 

 strong chemical affinity for decomposition, and of course the 

 reproduction of new compounds, many of which are soluble 

 in water, it would of course follow that the springs of this 



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