The Spanish monks had a station at Tupuquen, on the left bank of the river some four miles above El Callao, and prospectors from this settlement followed up the rich alluvial valley of a small tributary known as the Mocupia, founding there the settlement of Caratal, where there are still many prospecting shafts working free gold from a depth of about 20 feet, with the ruins of various mills erected at a later date, during the boom of the early eighties, including that of the notorious Callao Bis. From Caratal the prospectors spread over the surrounding country and found numerous rich deposits, the chief being El Callao, about two miles from Caratal. In 1842 a Brazilian named Pedro Ayares visited Tupuquen, and recorded the existence of auriferous sands in the river, but primitive washings were not established there till 1849, when good returns were obtained. After many years of prospecting and handwork the El Callao company was formed, and a mill was erected, yielding the following results:— ------+---------------+-----------------+----------------- Year. | Tons crushed. | Gold produced. | Average per Ton. ------+---------------+-----------------+----------------- | | Oz. | Oz. 1871 | 315 | 3,219·60 | 6·25 1874 | 3,963 | 17,187·68 | 4·33 1876 | 12,419 | 42,542·05 | 3·42 1878 | 9,673 | 49,638·88 | 5·13 1881 | 24,978 | 72,254·62 | 2·89 1884 | 30,936 | 177,055·16 | 5·72 1886 | 73,708 | 118,040·20 | 2·45 1889 | 57,301 | 52,971·35 | 0·91 1892 | 52,910 | 31,945·27 | 0·60 ------+---------------+-----------------+----------------- paying in dividends, from 1871 to 1892, 48,332,200 francs, or £1,933,288. Since that time little of importance has been done, and at the present time the mine is practically shut down, after having been involved in endless lawsuits.