Natural Sciences of Philadelphia ii 
When the writer arrived in Oruro, the celebration was still in 
progress. Of chief interest seemed to be the bull-fight, and most 
of the population was gathered at the bull-ring, or thickly scattered 
on the hill overlooking it. Belts of money are tied on a bull, which 
is let into the ring. Then, anyone who is desirous of increasing 
his wealth to the extent of a few centavos, is privileged to help him- 
self. Our sympathies are naturally with the bull, and when occa- 
sionally one turns and bowls over an Indian our interest increases, 
and we admit that it is not such bad sport after all. 
Oruro is the mining center of central Bolivia. Some distance 
to the southeast is the district of Huanuni which is of interest 
as furnishing the rare germanium-bearing minerals cylindrite and 
franckeite. Still farther southeast is Llallagua, the world’s greatest 
producer of tin. Adjacent to it are the similar mines of Uncia. 
Two days distant by mule are the old silver mines of Colquechaca. 
The road leads out from Uncia, across a pampa, towards the distant 
range. On the way, one meets many Indians trudging into Uncia 
for the Sunday market, some with considerable loads, others idling 
along, strumming carelessly on musical instruments made from the 
backs of armadillos. 
After a long day’s ride you arrive at a tambo. A tambo is a 
low building of adobe, with a thatched roof, and one or more 
rooms. On each side of the rooms is a couch of adobe brick. If 
you are not fortunate enough to carry a bed, the llama skins mas- 
querading as saddle blankets on the mules are thrown on the bricks. 
Late in the afternoon of the second day Colquechaca appeared in 
sight, and we were soon clattering down the old cobbled streets. 
The mines in former days were exceedingly rich in argentite, py- 
rargyrite and argyrodite. 
Potosi is the most celebrated mining district of Bolivia, as it is 
reputed to have produced over a billion ounces of silver. Accord- 
ing to the old Spanish laws, claims or boca-minas could be obtained 
for the modern equivalent of a few bolivianos per hectare. The 
holder of a boca-mina was permitted to tunnel in any direction 
until he ran into a tunnel belonging to someone else. As a conse- 
quence, mining on Potosi Mountain is a history of continual war- 
fare between the boca-minas. The visitor finds much of interest 
also in the great number of ornate old Spanish iglesias. At the 
colorful native market, the opportunity is presented of seeing types 
