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In the extreme violet there is a line, the fourth of hydrogen, also noted by Dr. Young, as one of the most frequent in the spectrum of the chromosphere, the wave-length of which is 410. Cornu thinks he has often perceived this line in the spectrum of the star, but he has not been able to measure it. The distinguished observer closes his account of these interesting researches as follows:

The readers of La Nature will permit us to add a few reflections of our own to those offered by our learned fellow-countryman. His reserve we acknowledge to be very wise, but he has expressed himself a little too strongly. Who, after perusing M. Cornu's analysis and the conclusions he has drawn, would not make the short step that here intervenes between fact and hypothesis, and assert the similarity, if not the identity, of the light of the star with that of the chromosphere? True, we cannot with certainty affirm that the apparently continuous faint spectrum in which are seen the bright lines was also its spectrum before it became visible to us, but that such is the case is highly probable. We cannot say what was the cause of this sudden development of gases, whose existence and incandescence are revealed by the star's spectrum, just as we are as yet unable to assign the cause of the sun's hydrogen protuberances. But is it nothing to class together phenomena, the only difference between which seems to be one of degree alone? The hypotheses of Huggins and Miller, as to the causes of the apparition of the star in the Corona Borealis, can of course never be verified; but no more can we verify the current hypotheses held by astronomers and physicists with regard to the presence of various chemical elements in the sun; we have here only probabilities. Such hypotheses, far from being of injury to science, are indispensable for its progress: they stimulate the observer's mind, constantly suggest to him fresh observations, and become a hinderance only when they are held to be demonstrated truths, and when men refuse to give them up after they have been proved to be erroneous, or after they have served their purpose.—La Nature.