22 COLORADO COLLEGE STUDIES. 



beds. The oxidation of ferrous sulphate, such as was 

 described as occurriny in the Ute Pass, gives rise to 

 sulphuric acid, and by subsequent reaction with car- 

 bonates to sulphates of the alkalies. The ferruginous 

 deposits in the broken silurian limestone indicate such 

 a reaction. 



8. The concentration of the solutions — that is, the large 



quantity of mineral matters contained in the spring 

 waters, comes evidently from prolonged contact with 

 rocks, such as would arise from percolation, and prob- 

 ably also from an increased solvent power of the water, 

 due to heat or pressure, or both combined. 



9. The difference in temperature of the several springs is 



remarkable as showing that either the waters come 

 from different sources, or if coming from the same 

 source have been cooled in an unequal degree by passing 

 through diverse strata, or through the influx of cooler 

 foreign waters. It was assumed under (2) above that 

 the most probable view was that the same water is made 

 to vary its content of dissolved mineral matters by the 

 admixture of other waters; and the variation in tem- 

 perature between the springs will be found on inspec- 

 tion of the table above to be in striking harmony with 

 this supposition. The temperature in general is lower 

 when the mineral content is lower, but it should be 

 remembered that the inflowing foreign waters may also 

 pass through strata so deeply buried as to be much 

 warmer than mere surface waters. 

 10. The variation of the springs between summer and winter, 

 in their contents of mineral matters dissolved, in the 

 quantity of water flowing from them, and in the volume 

 of gas yielded, together with the remarkable uniformity 

 of temperature throughout the year in some of them, 

 are evidently significant phenomena. The causes pro- 

 ducing them will be discussed in a subsequent para- 

 graph. 

 Before proceeding to deduce from the foregoing state- 

 ments a theory of the derivation of the carbon dioxide of the 



