1870.] DOUGLAS — ON OBSERVATIONS OF THE SUN. 125 



-with luxuriant elms; tlicre, of a Jcn^;cly intertwined tropical 

 forest, the intimately interwoven branches [spreading in all 

 directions, the prominences generally expanding as they mount 

 upwards, and changing slowly, almost imperceptibly." 



Intermediate between the chromospliere, yielding its spectrum 

 of bright lines, and the body of the sun — which gives a continuous 

 spectrum with dark lines, Father Secchi says — may, under favour- 

 able conditions of our atmosphere, be detected a continuous 

 spectrum. The explanation of this is not very easy, but the 

 following is suggested : If we suppose the body of the sun to be 

 liquid, the metals which compose it are in a state of fusion at a 

 white heat, and, therefore, emit w^hite light; if we suppose it 

 gaseous, the mass of glowing vapor is too dense to be transparent, 

 and, therefore, may act in the same manner as if it were liquid ; 

 but immediately outside this liquid, or gaseous nucleus, there is 

 a layer of ignited gases and vapors, situated so near the thin 

 outer limb of the orb as to be transparent, in which the vapors of 

 so many metals are burning, that their combined bright lines will 

 yield a continuous spectrum, or what may appear such. 



Another explanation, and a more probable one, because corro- 

 borated by experiment, has been oifered. A continuous spectrum, 

 according to Frankland and Lockyer, is given by gases when 

 undergoing condensation. Judging from what takes place in our 

 own atmosphere, "we may suppose, as Storey has pointed out, a 

 rapid condensation of certain of its constituents upon the surface 

 of the sun. Such a permanent gas as hydrogen would undergo 

 no change, and, therefore, continue burning beyond the limits of 

 the area of condensation. This area of condensation would form 

 a cloudy envelope, radiating back most of its heat to the sun, and 

 serving other purposes in the solar economy. Would the reversion 

 of the bright lines take place in this area ? 



There is not perfect unanimity of opinion as to the condition of 

 the body of the sun. The old idea of a solid nucleus is now 

 generally abandoned, and the opinion that it is liquid is yielding 

 to the views of those who conceive that at such a liigh tempera- 

 ture, as all admit, prevails, it must be gaseous. There are other 

 reasons still for believing it to be gaseous. In this latter case 

 there can be no well-detined atmosphere ; but the term may be 

 applied to the hydrogen or outer stratum of gas, and so much of 

 the deeper stratum as contains the vapors necessary to give the 

 Frauenhofer lines. The chromosphere in this view is that layer 



