By J. NORMAN LOCKYER.
IT is now exactly thirty years since the world rang with one of those discoveries which go down to the ages and at once insure the names of the makers of them being inscribed upon the muster-roll of the immortals. In the autumn of 1859, Kirchhoff and Bunsen announced that at last a way had been found of studying the chemical nature of bodies in space — nay, more, that they had already begun the work, and found that the sun, at all events, was built up of matter identical with that of which the earth is composed.
In physical science in most cases a new discovery means that by some new idea, new instrument, or some new and better use of an old one, Nature has been wooed in some new way. In this case it was a question of a new idea and an old instrument. The instrument was the spectroscope.
It forms no part of my present purpose to deal either with the principles involved in spectrum analysis or its history during the period which has elapsed since 1859. The task I have set myself in this article is a much more modest one.
First, I wish to point out that during the thirty years the method of work which Kirchhoff and Bunsen applied to the sun has been applied to the whole host of heaven. By this I do not mean that every star has been examined, but that many examples of each great class — nebula, comet, star, planet — have been studied. The same kind of information has been obtained with respect to these bodies as Kirchhoff and Bunsen gleaned with regard to the sun; and the great generalization to which I have referred has been found to hold good in the main for all. From nebulæ and stars existing in space in regions so remote that the observations have been of the utmost difficulty in consequence of the feebleness of their light; from comets careering through stretches of space almost at our doors, the same story has come of substances existing in them which are familiar to us here. In ascending thus from the particular to the general, from the sun to the most distant worlds, it is obvious that the field of observation has been enormously extended. Kirchhoff and Bunsen's view has been abundantly verified, as we have seen; but the question remains, Has this larger area of observation supplied us with facts which enable us to make a more general statement than theirs? It is possible that it has. Recent inquiry has suggested that if the study of meteorites be conjoined with that of the heavenly bodies, the story told by the spectroscope enables us to go a step further,