68 Scientific Proceedings, Royal Dublin Society. 
useless, except for mining, and is accordingly a retreat for the wild 
Tarahumare; 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, which, 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 con- 
taining 75 per cent. of bright metallic silver. Other neighbouring 
mines contain silver as sulphide. The mountains round Batopilas 
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 cover- 
ing. 
Leaving Batopilas 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 tothe Urique 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 existence of the volcanic dam). 
Nearly every kind of tropical fruit does well here. It is possible 
to go far up the valley near the river, a path having been blasted 
out by miners, for there is a large copper deposit near the turn of 
the great barranca, in a most inaccessible position. The valley 
extends a hundred miles above the town, and contains some old, 
rich, silver mines. We now proceed to Cerrocahui a small place on 
the temperate mesa, surrounded by arable land; here is an adobe 
church built in 1700. There are charming spots on the mesa, 
well wooded and level, with clear streams which end in a sheer 
descent of many thousand feet; from one, there is a view over 
the immense crags of the Arroyo Hondo. They are kept green 
