follows that when all other light is withdrawn, as Professor Hale's method enables him to withdraw it, the ordinary solar light remaining has become so much weakened that it can no longer overpower the beams from the prominences, and hence an image is printed on the photographic plate. Thus we can now obtain, not as heretofore merely isolated views of special prominences through the widely opened slit of the spectroscope, but we are furnished, after a couple of minutes' exposure, with a complete photograph of the prominences surrounding the sun. In Professor Hale's remarkable pictures, not only is every large prominence exhibited with ample detail, but the incandescent region of the chromosphere from which these prominences arise is also recorded with accuracy.
It may therefore be said that with this admirable process available the eclipse is no longer of much account for the purpose of instructing us as to the prominences. No doubt a pleasing picture of these objects may be afforded. Professor Pickering, indeed, describes them as of much interest on the recent occasion; but the attention of the eclipse observer in the present day is almost wholly otherwise directed.
For the corona is still only known to us by such opportunities as eclipses present. No doubt attempts have been made by photographic methods of various kinds to enable the corona to be brought within our scrutiny under ordinary circumstances. Up to the present, however, success cannot be said to have rewarded these efforts. The sunlight is so intense that if it be reduced sufficiently by any artifice, the coronal light also suffers so much abatement that, owing to its initial feebleness, it ceases altogether to be visible. We are therefore wholly depen-
