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In the consolidated mines, at a depth of 290 fathoms, thermometers sunk in a cross course of the rock (killas) indicated at the vein 92° and 88°; 10 fathoms from it, 86.3° and 85°; 24 fathoms from it, 85.3° and 84°. Here the metallic vein is the hottest part; Mr. Fox thinks, because of its allowing hot waters to ascend. The temperature 85.3° is at least 35° above that of the climate, and the ratio is consequently 1° in 49.6° feet; or, allowing 10 fathoms to the depth of variable temperature, 1° in 48 feet.

And still more lately, experiments made by Captain Oats inTresavean copper mine gave the following results.

Humboldt observed, in mines near Guanaxuato (Mexico),

The surface temperature is 16°. The volcanic character of the country is perhaps unfavourable for accurate inferences.

Saussure, in the salt mines of Bex, found

Mr. Hodgkinson, at the request of the British