Page:In the high heavens.djvu/90

 silvery corona which stretched from the sun to such a vast distance into the surrounding space. The corona, though a permanent append age of the sun, was only to be recognised when by the direct interposition of the moon the light of the sun was cut off, and in the gloom thus arising the radiance of the corona became readily and even brightly discernible. But the memorable discovery made by Janssen and Lockyer, independently, in 1868, showed that the prominences could be observed without the help of an eclipse, by the happy employment of the peculiar refrangibility of the rosy light which these prominences emit. This improvement in observational astronomy revolutionised the method of utilising eclipses. We are now so well acquainted with the forms of the prominences by the spectroscopic method that the eclipses have but little to teach us on that matter.

Of course it will be admitted that there are many circumstances with regard to these objects as to which we at present know but very little; however, we do not look in any considerable degree to eclipses for their solution. Quite recently a further extension has been given to the spectroscopic method of studying solar prominences by the beautiful invention of Professor Hale of Chicago. He has employed a very elaborate apparatus by which he is able, as it were, to sift out from the sunlight the beams of that particular refrangibility which astronomers would denote by saying that it belonged to the H line of the spectrum. With the light thus chosen Professor Hale obtains a photograph. It so happens that in the light of this particular hue—an invisible hue, it may be added, only perceptible to the peculiar sensibility of the photographic plate—the prominences are peculiarly rich. It