1856.] ANSTED— COBRE LODE. 151 



Temperature. — The temperature of the lode in the upper levels is 

 about 90" Fahr., both in the levels themselves, and wherever I could 

 place a thermometer in the rock. At ninety fathoms I noted in one 

 place a temperature of 96°, and in a small neglected working on the 

 south course of ore an exceptional temperature of 101°. At this 

 point, which was not without ventilation, being close to a shaft, the 

 heat was very sensible, but the air did not appear to be tainted with 

 any disagreeable odour. I noticed, however, much iron pyrites 

 thereabouts. Lower down, the air becomes much cooler, and in the 

 130-fathom level I observed the thermometer to stand at 86° in a 

 small sump near a slide, and at 88° in a hole opened in the rock, not 

 in the orey part of the vein. In many parts of the mine, both men 

 and boys work entirely naked, and although, while underground, I 

 did not notice much difference in the temperature, as compared with 

 deep mines in other countries, the subsequent exhaustion was far 

 greater than is usual in temperate chmates. The mines and district 

 are by no means unhealthy, although there has often been consider- 

 able mortality amongst the white (Cornish) hands, owing to the want 

 of prudence and caution whilst above ground. I was pleased to find 

 a cage provided in the Cobre mine to lift the miners after their 

 work was concluded. 



Recapitulation. — I may now sum up as follows the principal re- 

 sults of my observations on the western or productive part of the 

 Cobre lode. 



1. It includes three courses of ore regarded as distinct, nearly 

 parallel to each other in strike, but gradually approaching as they 

 go down, two of them unusually large and rich, and the third (the 

 middle) of smallest importance, the northernmost (on the foot-wall) 

 being chiefly affected by certain small heaves ; but all the orey 

 ground terminated by a cross course to the west. The intervals 

 between the three courses of ore are occupied by a conglomerate or 

 breccia, consisting of fragments of decomposing porphyries and 

 greenstone, abounding with lime, passing into a compact whitish 

 green porphyry. Associated with the courses of ore, the veinstone, 

 and the country, are large quantities of iron pyrites, and at a certain 

 considerable depth the veinstone contains gypsum. 



2. Regarding the three courses of ore together as parts of one 

 great lode, nearly 200 yards wide at its crop, this lode may be de- 

 scribed as dipping moderately to the south, as shown in fig. 4, p. 148, 

 the orey portions being chiefly near the hanging-wall and the foot- 

 wall, but extending occasionally and irregularly not only into bunches 

 and strings in the intervening veinstone, but also into the country, 

 both north and south of the lode. The whole of the adjacent rock 

 is also highly mineralized. 



3. Not only the lode, but each of the principal courses of ore 

 appears to be well indicated at the surface by a distinct gossan, con- 

 sisting of spongy quartz and iron oxide of the usual kind, and 

 highly coloured clays and marls, immediately beneath or amongst 

 which have been oxides, carbonates, and sulphurets of copper. At 

 greater depth, the yellow ore (a sulphuret of copper and iron) en- 



