PHILOSOPHICAL SOCIETY OF WASHINGTON. 73 



Mr. W. B. Taylor read a paper on 



THE TEMPERATURE OP SPACE. 



Mr. Taylor remarked that, although this title was derived from 

 the illustrious Fourier, and was in general use, it was obviously 

 not very accurate; and that perhaps the designation "star-heat" 

 would be less objectionable, as being the nearest analogue to 

 star-light. 



Fourier supposed that this temperature could not be much 

 less than the coldest degree observed in polar regions, and esti- 

 mated it at — 58° F. PoissoN, following in his track, adopted 

 essentially the same views and the same estimate ; suggesting, 

 however, that in the course of one million years the solar system 

 might have passed from an external temperature of +100" C. to 

 that of — 100° C. — a demonstrably impossible occurrence. 

 PouiLLET (in 1838) estimated the "temperature of space at 

 — 224° F. Hopkins (in 1855) placed this temperature as high 

 as — 39° F. And Sir John Hersohel (in 1857) made an esti- 

 mate somewhat lower than that of Pouillet, or — 239° F. 



Eminent as these names are, their results are very discordant, 

 and' are all based on assumptions of great improbability. Remem- 

 bering our own equatorial "snow-line," and our tropical ice- 

 clouds, at no greater elevation than three or four miles, it seems 

 quite incredible that in open space, unprotected by any atmo- 

 sphere, mercury could be melted (at 91,000,000 miles) even under 

 the direct blaze of the sun. And this is about the temperature 

 assigned by Hopkins to star-heat alone. 



Mr. Taylor concluded that we have really no reason for sup- 

 posing that the heat radiated to us from the stars bears any 

 higher ratio to the heat received from the sun, than star-light 

 bears to sun-light; and that as the whole amounfof light received 

 from the stellar vault on both hemispheres does not probably 

 exceed the ten-millionth of that received from the sun, the heat 

 being in the same proportion, even Herschel's estimate (the 

 lowest here cited) must be pronounced enormously too high ; and 

 the star-heat, commonly called the "temperature of space," can- 

 not be much above the absolute zero. 



Mr. Newcomb followed with some remarks, concurring in these 

 views. 



