lO ABOUT VOLCANOS AND EARTHQUAKES. 



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 v/ells) 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 

 Grenelle. 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, 710 vian, but 

 a mass of red-hot iron. Just so with the outside crust of 



