THE INTERIOR OF THE EARTH. 453 



peacefully coexist. Nothing is surer than that all the inventions, and 

 improvements, and discoveries, of which our time is so fruitful, are 

 tending with irresistible force to carry mere political democracy into 

 anarchy. 



All these evidences of growing social and political discontent, all 

 these agitations and disturbances the more violent talk on the one 

 side, the leaning to repression on the other are indications of unstable 

 equilibrium, of a maladjustment of powerful forces. It is the necessity 

 of the time the vital, pressing necessity that these phenomena re- 

 ceive the careful, conscientious attention of thoughtful men, who will 

 trace them to their source and popularize the remedy. It will not do 

 to leave them to the ignorant poor and the ignorant rich, to politicians 

 and demagogues. They require the scientific spirit and the scientific 

 method ; they demand the thought of those who can think, and whose 

 opinions carry weight. 



THE INTERIOR OF THE EARTH* 



By R. RADAU. 

 II. 



ASIDE from the evidences of the earth's internal heat furnished 

 by artificial excavations, we have incontestable proof thereof in 

 hot springs and in volcanic phenomena generally. The temperature 

 of certain springs is nearly 100 at the surface. That of the Chaudes- 

 Aigues is 80 ; the Trincheras (Venezuela), 97 ; the geysers of Ice- 

 land are 85 at the surface and 127 at a depth of twenty metres. But 

 it is plain that the temperature of hot springs does not necessarily indi- 

 cate the heat of the depths they come from. Aside from purely chemi- 

 cal agencies, there are physical causes sufficient to account for a very 

 hisrh degree of heat. When we consider the size of such caverns as 

 those of Carniola and Istria, it will not be difficult to believe that there 

 may be in the earth's crust fissures ten or twenty kilometres in depth, 

 that may be filled with water, like the cavity that pei-iodically absorbs 

 and expels the water of the Lake of Kirknitz. Even at a depth of two 

 or three kilometres the temperature of this water is 100, but the pres- 

 sure of two or three hundred atmospheres which it sustains prevents 

 ebullition, as at 100 steam attains a pi-essure equal to the weight of 

 only one atmosphere, and it does not form unless the pressure exceeds 

 that. Under stronger pressure a higher temperature is required before 

 ebullition takes place (i. e., the temperature at which the pressure of 

 steam equals the resistance, or pressure on the liquid). Thus, under a 



* Translated from the " Revue des Deux Mondes," by Guy B. Seely. 



