272 TRAySACTIOXS OF THE A-VEIUCAX IXSTITUTE. 



It was once tliouglit tliat an exterior sliell, snrrounding the true 

 body of the sun, was the source of \\U Yv^\\t and heat, and that 

 within this shell was a comparatively C0(jl, dark hody, wliich might 

 possibly be inhabited by beings not very unlike ourselves. Now 

 that we know the case to be otherwise, and that the interior of the 

 sun must be at a temperature surpassing that of the fiercest fires 

 wliich can be produced by human art, the question of habitability 

 loses its significance, except, perhaps, from a theological point of view, 



Bnt a consideration which might well have been borne in mind, is 

 tlie vastly greater weight whicli all objects at the sun must exhibit 

 by reason of the attraction of his immense mass. A man of ordinary 

 size would there weigh nearly 5,000 pounds, and although we may 

 hardly indorse the younger Ilerschel's statement " that he would be 

 crushed as flat as a pancake by his own weight," we must concede 

 that it would be a somewhat fatiguing exercise for him to run up and 

 down stairs very often, and that the sun's surfiice would he rather a 

 hard road to travel. 



The Sun's Heat. 



The sources of tlie light and heat of the sun, the only two of his 

 raarvelons properties a})parent to the ordinary observer, are problems 

 the greatest difficulty. I will only say here that the most vivid light 

 developed by human art, when interposed between the eye and the 

 sun, appears like a black spot upon the solar disk, the highest tempera- 

 ture yet produced by man is that evolved by the combustion of char- 

 coal in oxygen, which Bunsen estimates at 10,000^^ C, or 18,000^ F. ; 

 and this is about five-sevenths of the lowest reasonable estimate for 

 the tem])erature of the solar surface. Coal burning at the rate of 

 one pound to the scpi are foot in about two seconds would attain this 

 temperature, and Rankine has estimated that in the furnaces of power- 

 ful locomotive engines, a pound of coal to each square foot of grate 

 surface is consumed in from thirty to ninety seconds, yielding a heat 

 from one-fifteenth to one-forty-fifths as intense as that at the surface 

 of the sun. 



Ado])iing his estimate that a heat equal to that emitted by the 

 sun might l>e attained i)y the combustion of coal at this rate of one- 

 half pound per sec(»nd to the square foot, it is easy to find how long 

 the whole mass of the sum would last, were it composed of coal burn- 

 ing at that rate, and furnished moreover with an unlimited su})])ly of 

 oxygen to supj)ort the coml)ustion. Performing the calculation, we 

 find that tiie entire sun would be consumed in a little more than 



