66o TEE POPULAR SCIENCE MONTHLY. 



secondly his preconceived ideas as to what he was likely to see, for 

 otherwise the value of his observations will not be fully aiDpreciated. 



Our readers may perhaps remember that in the year 1870 a discus- 

 sion took place on the question whether the glory of light seen around 

 the sun during total eclipse belongs to the sun or not. There were 

 those who maintained very confidently the opinion that this glory is 

 either a purely optical phenomenon only or else is due to the passage 

 of the solar rays through our own atmosphere all round the place of the 

 eclipsed sun. On the other hand, there were some (ourselves among 

 the number) who pointed out that the corona must necessarily belong 

 to the sun, since its features could not possibly be reconciled with any 

 other theor}". The greater number of astronomers seemed, however, to 

 form no opinion one way or the other, but to prefer to leave the matter 

 to be decided by fresh evidence. For too many imagine that the best 

 way of showing how greatly they value observations is by declining to 

 investigate the full significance of observations already made. 



It will be remembered that before long the new observations de- 

 vised to settle a question which had been abundantly answered by ob- 

 servations already made proved unmistakably the solar nature of the 

 corona. Photographs were taken during the total eclipse of December, 

 1870, and in greater number during that of December, 1871. On the 

 latter occasion photographic views of the corona taken at stations far 

 apart agreed closely together, showing that the corona could not pos- 

 sibly be an atmospheric phenomenon. No one could imagine that the 

 air above Baicull, where Mr. Davis (Lord Lindsay's photographer) took 

 his views, could by some amazing accident produce coronal features re- 

 sembling those jDroduced by the air above Ootacamund, one station 

 being close to the seashore, the other hundreds of miles inland and 

 some 10,000 feet above the sea-level. On the other hand, the resem- 

 blance of the several views taken at either station showed that the 

 coronal glory could not be due to the illumination of some matter on 

 the hither side of the moon, but far outside our own atmosphere. For 

 the solar rays, passing athwart the lunar disk to fall upon such matter, 

 Vv-ould shift rapidly in position as the moon moved onward, so that the 

 features seen at the beginning of total eclipse would diifer markedly 

 from those seen toward the end. Since the six pictures taken at Baicull 

 closely resembled each other, as did the six taken at Ootacamund, so 

 that all twelve views represented the same corona (though of course 

 not all to the same distance from the sun), it was manifest that the 

 corona then seen was a solar appendage. The actual distance to which 

 the corona can be traced in these pictures corresponds to about 900,- 

 000 miles. 



But the believers in an atmospheric corona were not even yet wholly 

 satisfied. Nay, before the recent total eclipse one among them even 

 went so far as to say that the observations and photographs of 1870 

 and 1871, while demonstrating the solar nature of the glory immedi- 



