Page:Popular Science Monthly Volume 14.djvu/678

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secondly his preconceived ideas as to what he was likely to see, for otherwise the value of his observations will not be fully appreciated.

Our readers may perhaps remember that in the year 1870 a discussion 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 theory. 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 devised to settle a question which had been abundantly answered by observations 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 possibly 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 resembling those produced 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 resemblance 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, would shift rapidly in position as the moon moved onward, so that the features seen at the beginning of total eclipse would differ 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-