1882.] On the Recent and Coming Total Solar Eclipses. 299 



19. I next pass to another point on which an observation was made 

 in Egypt. 



20. In fig. 4 we considered the sun's atmosphere, taking the simplest 

 case, that of one element ; when the sun cools it will be a very complex 

 mass chemically. If the laws of evolution hold we need not expect 

 that this will largely increase the complexity of the hottest layers A 

 and B, but higher up, say at H — L, the complexity of chemical forms 

 produced by evolution along the fittest lines will be very consider- 

 able. 



21. These strata H — L may be taken to represent the corona. Its 

 spectrum, therefore, should not be a continuous one, but should con- 

 sist of an integration of all the radiations and absorptions of these 

 excessively complex layers. 



22. The spectrum of the corona as I saw it in Egypt exactly 

 answered to this description. Instead of the gradual smooth toning- 

 seen, say in the spectrum of the limelight, there were maxima and 

 minima producing an appearance of ribbed structure, the lines of 

 hydrogen and 1474 being, of course, over all. This observation, how- 

 ever, requires confirmation, for the look I had at the corona spectrum 

 was instantaneous only. 



23. This observation should certainly be repeated during future 

 eclipses with the proper instrumental conditions, i.e., small, intensely 

 bright image on narrow slit and spectroscope of small dispersion. I 

 believe that, under these conditions, photographs could readily be 

 obtained with the new plates. 



24. Now an eclipse occurs next May at a critical time of the sun's 

 activity, for, so far as we can see, we shall be nearly at sun-spot 

 maximum, and I hold that it will be a disgrace to our nineteenth 

 century science if efficient steps are not taken by those who are 

 regarded as the leaders of science in this and other civilised countries 

 to secure adequate observations. 



25. So far I have only referred to those special observations under- 

 taken this year to discriminate between two rival hypotheses, but 

 both hypotheses may be wrong in many points, so that we must not 

 limit ourselves to such observations, but collect facts over the whole 

 field, as has always been the custom in eclipse expeditions. 



26. In my opinion the following scheme shows the observations 

 which, in the present state of our knowledge, it is most desirable to 

 secure. The scheme, I am aware, is by no means exhaustive. I give 

 the observations in the order of importance I attach to them, having 

 regard to the present position of solar theory and the conditions of 

 eclipse observations. 



(1.) 6-inch equatorial of long focus, perfect clockwork, spectroscope 

 with dispersion of at least five prisms of 60°. 



Clamp point of disappearance of sun at base of normal slit, and 



