Fi co sa 
166 J. P. Kimball on the Silver Mines of Sta. Eulalia, Mexico, , 
impart a concretionary appearance, or, as if limestone breccia 
were cemented by ferruginous ore. In such places the beds, are 
not brecciated, but thus strikingly indicate the energy of disin- 
tegrating and segregating action under the decomposition or 
oxydation of iron salts (probably proto-carbonate) origin 
ural caverns, together forming underground spaces scarcely less 
imposing than the most noted caves that excite the wonder of 
tourists. 
_ The mines of Santa Eulalia are scattered all over the great 
limestone uplift, and along the deep ravines which have scored 
between the Dolores Cafion on the northwest, and on the south- — 
bs oa waters of the arroyo in which is the village of Santa 
ualia. 
the formation is seen rapidly declining in the ravine tow 
mouth, and the i cantera is thus brought down so as 
to form » e hills) The limestone altogether dis- 
appears from above the bed of the rayine within a few hundred 
of this formation, though the surface is immediately overspread 
by the cemented ru 6 eek edhe J The bills on either 
