12 INTERNAL HEAT OF THE EARTH. 



Chimborazo, 21,440 ; Illimani, 24,450 feet ; and Sorota, 25,000. The high- 

 est mountain in the world is in Asia, the Himalaya, which rises 26,862 feet 

 above the level of the sea. 



4. The surface of the earth has not always possessed the same 

 configuration that it now presents ; it has been frequently upturned, 

 and there is even reason to believe that the entire globe was a 

 liquid mass, melted by heat, and that it gradually became solid as 

 it cooled. 



5. Except at comparatively shallow depths, we cannot examine 

 the nature of the materials constituting our globe, not even hy 

 Descending into mines, excavated for the purpose of extracting the 

 wealth they contain ; for the deepest of these excavations do not 

 exceed 500 yards. But by calculations, it has been inferred that 

 the centre of the earth cannot be occupied, either by water, or by 

 vapour, but by matter as heavy as our heaviest metals, and so hot 

 that it is probably in a state of constant fusion. 



6. A great number of facts concur in proving that the earth 

 possesses an internal heat (the remnant of its original heat), inde- 

 pendent of that which it receives from the sun. Its temperature 

 increases in proportion as we descend to considerable depths ; 

 there are some very deep mines in which the workmen can only 

 labour when naked, and wherever the water of a spring rises from 

 a great depth, its temperature is always very high. This increase 

 of temperature has even been measured, and it has been ascer- 

 tained that the heat of the earth increases about two degrees, Faren- 

 heit, for every 70 to 100 feet. In very deep cellars, where the 

 influence of the seasons is not felt, and where the temperature is 

 always the same, the thermometer, at Paris, stands at about 51 

 degrees, and at a depth of 200 feet below these cellars the heat is 

 about 55 degrees ; at a league below the surface, the temperature 

 must be above that of boiling water, and at a depth of less than 

 two leagues, it must be sufficient to melt tin. 



7. It appears to be demonstrated, that the globe, at some remote 

 period, was in a state of incandescence, or liquefaction from heat, 

 and that it cooled by degrees ; but we must not conclude that this 

 cooling process has continued to the present time, and is still going 

 forward ; it has almost, if not entirely, ceased. From the earliest 

 records of history, to the present moment, the temperature of the 



4. Has the surface of the earth always been the same in form and shape 

 as it now is ? Is it supposed that the globe has always been in its present 

 condition ? 



5. What occupies the centre of the earth ? 



6. Is the temperature of the earth the same at its centre as it is on the 

 surface ? What reasons lead us to the conclusion that the earth possesses 

 an internal heat? 



7. Is it supposed that the earth is becoming cooler and cooler every day T 

 How is the earth enabled to preserve its temperature ? 



