109 



of volcanoes is traversed, the highest being the Cerro de San Juan; their 

 form is rounded on top, but with steep slopes, and the lava is a dark ba- 

 sic material full of green spherules, which are not much elongated in any 

 direction; this lava appears to have been exuded in a pasty condition, for 

 it shows no signs of bedding or flow. The river has cut a narrow winding 

 gorge through it, with steep but not vertical sides Above San Juan de 

 Dios, at San Ignacio, is the junction of the Batopilas river, in a more open 

 eoxmtry; also showing some signs of alluvial deposits. 



The Batopilas river flows between steep cliffs of basalt and diorite, 

 apparently lower members of the great plateau series, and not recent erup- 

 tions like those of San Juan and Realito. Near Puebla, granite with nu- 

 merous dykes and patches of schorl is exposed; and generally the great 

 variety and numerous sections of the rocks in this district would make 

 it interesting te a geololist, who had time to study them. On occount of its 

 ruggedness it is useless, except for mining, and is accordingly a retreat 

 for the wild Tarahumara; whose dark red forms may be seen bathing in 

 the river, and at night the light of fires in the caves they inhabit, gleams 

 in the lofty recesses of the hills. 



Batopilas is a considerable mining town, its mineral veins have been 

 worked since the early years of the Spanish occupation, and they are now 

 exploited by a United States company, wioh, alone out of many mining 

 concerns in these provinces, uses modern methods and machinery. The 

 principal veins are of crystallized native silver imbedded in calcite, the 

 country rock being a hard diorite. One mine extends 900 feet above, and 

 the same depth below the adit; and the author saw a blast fired in a vein 

 one foot wide containig 75 per cent, of bright metallic silver. Other neigh- 

 bouring mines contain silver as sulphide. The mountains round Batopi- 

 las have been stripped of their wood for fuel at the mines, and when seen 

 from above appear covered with a ramifying network of small ravines, by 

 which the whole surface is made steep, the slopes from two arroyos always 

 terminating in a sharp ridge; this extreme effect of denudation may be 

 due to removal of the natural covering. 



Leaving Batopillas we reach the Cerro Colorado, an immense red mass 

 of low grade, auriferous rock; it was recently worked on a considerable 

 scale at a loss, and the machinery is still on the spot; costly transport was 

 the chief obstacle to success. We now cross over the cordon to the Uri- 

 que valley, and go up to the town; although the rock walls are 5000 feet 

 high, and very precipitous, the valley has a narrow flat floor composed of 

 alluvial materials deposited under water (during the existance of the vol- 

 canic dam). Nearly every kind of tropical fruit does well here. It is pos- 

 sible to go far up the valley near the river, a path having been blasted 



