Familiar lectures on scientific subjects / by Sir John F.W. Herschel.

  • Herschel, John F. W. (John Frederick William), 1792-1871.
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Familiar lectures on scientific subjects / by Sir John F.W. Herschel. Source: Wellcome Collection.

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    if we had a shaft sunk a mile deep, we should find in the rock a heat of 105°, which is much hotter than the hottest summer day ever experienced in England. (14.) It is not everywhere, however, that it is worth while to sink a shaft to any great depth ; but borings for water (in what are called Artesian wells) are often made to enormous depths, and the water always comes up hot; and the deeper the boring, the hotter the water. There is a very famous boring of this sort in Paris, at La Crenelle. The water rises from a depth of 1794 feet, and its temperature is 82° of our scale, which is almost that of the equator. And, again, at Salzwerth, in Oeyn- hausen, in Germany, in a boring for salt-springs 2144 feet deep, the salt water comes up with a still higher heat, viz., 91°. Then, again, we have natural hot-water springs, which rise, it is true, from depths we have no means of ascertaining ; but which, from the earliest recorded times, have always maintained the same heat. At Bath, for instance, the hottest well is 117° Fahr. On the Arkansas River, in the United States, is a spring of 180°; which is scalding hot; and that out of the neigh- bourhood of any volcano. (15.) Now, only consider what sort of a conclusion this lands us in. This globe of ours is 8000 miles in diameter; a mile deep on its surface is a mere scratch. If a man had twenty greatcoats on, and I found under the first a warmth of 60° above the external air, I should expect to find 60° more under the second, and 60° more under the third, and so on; and, within all, no man, but a mass of red-hot iron. Just so with the outside crust of