296 



Mr. J. N. Lockyer. 



[Nov. 23, 



(4.) The germs of iron are distributed among the various strata 

 according to their heat-resisting properties, the most complex at L,. 

 the least complex at A. 



(5.) Whatever process of evolution be imagined, as the temperature 

 runs down from A to L, whether A, 2A, 4A; or A + B, 2[2(A + B)], 

 or X + Y + Z, the formed material or final product is the work of the 

 successive associations rendered possible by the gradually lowering 

 temperature of the successive strata, and can therefore only exist at L. 



10. Now at this point a very important consideration comes in. 

 It was stated (in 6) while discussing the conditions of observation, 

 that whether we were dealing with strata of substances extending 

 down to the sun or limited to certain heights, the spectral lines would 

 always appear to rest on the solar spectrum, and that the phenomena 

 would in the main be the same. 



11. This, however, is true in the main only, there must be a 

 difference, and this supplies us with a test between the rival hypotheses 

 of the greatest stringency. The stratum B, being further removed 

 from the photosphere than the stratum A, will be cooler, its lines 

 therefore will be dimmer, and the lines of C will be dimmer than the 

 lines of B, and so on. So if we could really observe the strata, the 

 longer a line is, i.e., the greater the height at which the stratum 

 which gives rise to it lies, the dimmer the line will be. 



12. Now our best chance of making such an observation as this is 

 during a total eclipse. We do not see the lines ordinarily in conse- 

 quence of the illumination of our air. As during an eclipse before 

 totality the intensity of this illumination is rapidly diminishing, the 

 lines first visible should be short and bright, and should remain short 

 while the new lines which become visible as the darkness increases 

 should be of gradually increasing length, so that the spectrum should 

 become richer in the way indicated in fig. 5. 



13. Further, the lines in 1 should be lines seen in prominences, 

 and not in spots, and relatively brighter in the spark than in the 

 arc, while the longer lines added in 2 and 3 should be lines affected in 

 spots, and not in prominences. 



14. All these phenomena were predicted for the Egyptian eclipse a 

 year before its occurrence, and were verified to the letter for the lines 

 of iron over a purposely limited region. 



15. The actual observations of the iron lines made at Sohag are 

 shown in the accompanying map, and these actual observations are 

 contrasted with the lines thickened in spots, the lines observed in the 

 prominences by Tacchini, those intensified on passing from the arc to 

 the spark. The Fraunhofer lines are also given according to 

 Angstrom and Yogel, and the iron spectrum of the arc and spark 

 according to Angstrom and Thalen. The observations during the 

 eclipse were made 7 minutes, 3 minutes, and 2 minutes before 



