Intelligence and Miscellaneous Articles. 159 



sophy in the University of Glasgow ; and it has been shown as a 

 first result, that there certainly is sodium in the suns atmosphere. 

 The recent application of these principles in the splendid researches 

 of Bunsen and Kirchhoff (who made an independent discovery of 

 Stokes's theory), has demonstrated with equal certainty that there 

 are iron and manganese, and several of our other known metals in the 

 sun. The specific heat of each of these substances is less than the 

 specific heat of water, which indeed exceeds that of every other 

 known terrestrial solid or liquid. It might therefore at first sight 

 seem probable that the mean specific heat of the sun's whole sub- 

 stance is less, and very certain that it cannot be much greater, than 

 that of water. But thermodynamic reasons, explained in the paper, 

 lead to a very different conclusion, and make it probable that, on 

 account of the enormous pressure which the sun's interior bears, his 

 specific heat is more than ten times, although not more than 10,000 

 times, that of liquid water. Hence it is probable that the sun cools 

 by as much as 14° C. in some time more than 100 years, but less 

 than 100,000 years. 



As to the sun's actual temperature at the present time, it is 

 remarked that at his surface it cannot, as we have many reasons for 

 believing, be incomparably higher than temperatures attainable arti- 

 ficially at the earth's surface. Among other reasons, it maybe men- 

 tioned that he radiates heat from every square foot of his surface at 

 only about 7000 horse-power. Coal burning at the rate of a little 

 less than a pound per two seconds would generate the same amount ; 

 and it is estimated (Rankine, 'Prime Movers,' p. 285, edit. 1859) 

 that in the furnaces of locomotive engines, coal burns at from 1 lb. 

 in 30 seconds to 1 lb. in 90 seconds per square foot of grate-bars. 

 Hence heat is radiated from the sun at a rate not more than from 

 fifteen to forty-five times as high as that at which heat is generated 

 on the grate-bars of a locomotive furnace, per equal areas. 



The interior temperature of the sun is probably far higher than 

 that at the surface, because conduction can play no sensible part 

 in the transference of heat between the inner and outer portions of 

 his mass, and there must be an approximate convective equilibrium of 

 heat throughout the whole ; that is to say, the temperatures at dif- 

 ferent distances from the centre must be approximately those which 

 any portion of the substance, if carried from the centre to the surface, 

 would acquire by expansion without loss or gain of heat. 



Part II. On the Origin and Total Amount of the Swi's Heat. 

 The sun being, for reasons referred to above, assumed to be an 

 incandescent liquid now losing heat, the question naturally occurs, 

 how did this heat originate ? It is certain that it cannot have ex- 

 isted in the sun through an infinity of past time, because as long as it 

 has so existed it must have been suffering dissipation ; and the finire- 

 ncss of the sun precludes the supposition of an infinite primitive store 

 of heat in his body. The sun must therefore either have been created 

 an active source of heat at some time of not immeasurable antiquity 

 by an overruling decree ; or the heat which he has already radiated 

 away, and that which he still possesses, must have been acquired by 

 some natural process following permanently established laws. With- 

 out pronouncing the former supposition to be essentially incredible, 



