Pee he : " 4 
ae ? J. P. Kimball on the Silver Mines of Sta. Eulalia, Mexico. 165 
in the surrounding hills, which rise to the height of some 800 
feet above the plain. - © 
A curious Uthological phenomenon, though in a less con- 
spicuous way not uncommon in other localities which I visited 
in Chihuahua, is a formation of conglomerate which is found 
on all the slopes of the district, and which incases the lower 
and middle portions of the hills ‘like a shell.* Thi 
dently been formed by carbonated caleareo-magnesian infil 
tions, springing from the summit cantera; and, penetrating the 
fine and coarse detritus of the surface alike, have cemented it, 
and thus produced all the gradations from a fine friable sand- 
stone to a coarse breccia. The village rests upon it. age the 
main street it is distinctly bedded, and cleaved by joints. No- 
where is it found entering into the interior structure of the hills, 
and no traces of it are found in steep places, Yet cursory 
region is in the S anto heegein mine. All the rest of the 
deposits ae more or less irregular, and in a varie 5 fancies of 
occurrence, are contained in the nearly horizontal fossiliferous 
strata Wroteesaisy All the strata apts water level = 
exceedingly cavernous. In nearly all of the workings, ca 
entirely shut off from the surface eran encountered. sacs 
of these are of enormous size. The t cave of the Parcionera 
and San José mines, is said to be large enough to hold the 
Wage of Chihuahua. Though una ne es or. its height, 
to illumine its roof, I am lieve this. Drusy 
cavities or vugs of all sizes, es the © ie exhibitions of 
€ same prevailing cavernous character. These latter yield 
rena pockets of ore. Rich bonanzas have been ot from 
i ; 
the chloro-bromid (embolite) and to 1odid (iodyrite) of i eae ee 
Very ferruginous, to which circumstance they owe their oer 
= also, to a considerable » degre’, the 
which a have ‘been dep ae are always 
and 1. f beddi pi spain! son) 
es oe sometimes iene oh all ‘cons modes of pad 
rence, without order or defined limits. A bed, or a n 
ber of bet: of the limestone, in places ma be thoroughly 
Webbed with such segregations of so decided a character as to 
* This Jour., xiviii, p. 382. 
