20 TRANSACTIONS OF THE [OCT. 18^ 



thing more than a summary of the facts upon which this state- 

 ment rests, but I may say that they are so numerous and signi- 

 ficant that the conclusion deduced from them, enunciated in 

 the above paragraph, is not only convincing, but inevitable. I 

 will briefly notice some of these facts. 



From observations in mines, and from deep borings, from hot 

 springs and volcanoes, we have learned that the interior of the 

 earth is intensely hot. The most satisfactory data for this con- 

 clusion are furnished by wells and mines. These are located in 

 all the great divisions of the earth^s surface; China, India, Aus- 

 tralia, Africa, Europe, and North and South America, all have 

 their mines or deep borings, which give fairly harmonious testi- 

 mony upon this subject. They prove that after passing the 

 plane of invariable temperature, beyond which the alternations 

 of the seasons are not felt, the heat increases about 1° Fahr. for 

 every fifty feet; for example, the well in the grounds of the 

 Lunatic Asylum at St. Louis is 3,843 feet in depth; at 3,200 

 feet, where the temperature was last observed, it was 107°; the 

 State House well, at Columbus, Ohio, is 2,775 feet deep, and at 

 2,575 feet the temperature is 88°. The artesian well at Louis- 

 ville, Kentucky, is 2,080 feet deep, and the temperature at the 

 bottom is 82°, summer and winter. Other wells bored in the 

 Valley of the Mississippi and in the Eastern States furnish sim- 

 ilar data. 



In Europe, many deep mines and wells have afforded facts co- 

 incident with those I have reported from this country ; for ex- 

 ample, the well of Grenelle, at Paris, is 1,800 feet deep, and the 

 water which flows from it has a temperature of 82° Fahr., while 

 the mean annual temperature at the surface is 51°. A well bored 

 at Sperenberg, Germany, to the depth of 4,172 feet has a tem- 

 perature, at 3,390 feet, of 115.5° Fahr., while a well at Schladen- 

 bach, 5,286 feet deep, has a temperature at bottom of about 131°. 

 Wells in China, India, and Australia show a corresponding in- 

 crease of temperature in descent, although few quantitative ob- 

 servations have been made there. 



There are some exceptions to the rule that the temperature 

 increases at the rate of 1 degree for every 50 feet in descent; for 

 example, in the mines on the Comstock Lode, Nevada, at the 

 depch of 3,200 feet the temperature is 160° Fahr., an increase of 

 about 1 degree for every 29 feet of descent. This case and simi- 

 lar ones at Monte Massi, in Tuscany, and at Buda-Pesth, Hun- 

 gary, are quoted by Professor Judd, in his Volcanoes, and are 

 considered of sufficient importance to invalidate the evidence of 

 thousands of other mines and wells. But the exceptions only 

 prove the rule. The wells mentioned are located in regions 

 which not long since, geologically speaking, have been the 



