2S-1 THE NEBULAE HYPOTHESIS. 



&quot;most of necessity. Thnt an d priori inference which prob 

 ably seemed to many readers wildly speculative, should be 

 thus conclusively justified by observations, made without 

 reference to any theory, is a striking fact ; and it gives yet 

 further support to the hypothesis from which this d priori 

 conclusion was drawn. It may be well to add that Kirch 

 hoflf, to whom we owe this discovery respecting the consti 

 tution of the solar atmosphere, himself remarks in his me 

 moir of 1801, that the facts disclosed are in harmony with 

 the Xebular Hypothesis. 



And here let us not omit to note also, the significant 

 bearing which KirchhofFs results have on the doctrine con 

 tended for in a foregoing section. Leaving out the barium, 

 copper, and zinc, of which the quantities are inferred to be 

 small, the metals existing as vapours in the Sun s atmo 

 sphere, and by consequence as molten in his incandescent 

 body, have an average specific gravity of 4 25. But the 

 average specific gravity of the Sun is about 1. How is 

 this discrepancy to be explained ? To say that the Sun 

 consists almost wholly of the three lighter metals named, 

 would be quite unwarranted by the evidence : the results 

 of spectrum-analysis would just as much warrant the asser 

 tion, that the Sun consists almost wholly of the three heav 

 ier. Three metals (two of them heavy) having been al 

 ready left out of the estimate because their quantities ap 

 pear to be small, the only legitimate assumption on which 

 to base an estimate of specific gravity, is that the rest are 

 present in something like equal amounts. Is it then that 

 the lighter metals exist in larger proportions in the molten 

 mass, though not in the atmosphere ? This is very un 

 likely : the known habitudes of matter rather imply that 

 the reverse is the case. Is it then tlrat under the condi 

 tions of temperature and gravitation existing in the Sun, 

 the state of liquid aggregation is wholly unlike that exist 

 ing here ? This is a very strong assumption : it is one for 



