The Evolution of the Sciences 



Father Secchi, in 1875, found it reasonable to be 

 satisfied with half that figure, whereas Pouillet, 

 and in 1875 Violle, decided for a temperature of 

 1500 C. Later observers have, however, come 

 to an agreement ; the researches of the American 

 physicist, Langley, have led to more reliable 

 determinations. By relying on the quality and 

 distribution rather than the quantity of the 

 different radiations which bodies emit according 

 to their temperature, a value of 7000 has been 

 found for the sun's approximate temperature. 



When we remember that the temperature of 

 a casting of molten steel is roughly 1800 centi- 

 grade, and that the electric arc, in its hottest 

 part, reaches 4000, we can understand that 

 while the probable temperature of the sun is 

 higher than any obtainable in a laboratory it is, 

 however, not too remote for us to form an idea 

 of the properties of matter at such a tempera- 

 ture. If the sun's temperature were of the order 

 suggested by Waterston and Secchi all hope 

 of positive knowledge concerning its nature 

 would have vanished. Even now we must 

 remember that nothing is known regarding the 



temperature of the sun's interior. Langley's 



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