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 comprehend adequately the enormous accession to our knowledge which this indicated. Chemists had studied the structure of our globe for centuries; they had ascertained that it was composed of some sixty or seventy elements; but they knew nothing as to the composition of the heavenly bodies. The sun, moon, and stars might, for anything we knew at that time, be composed of elements quite as unknown to us as lithium or any other rare metal was to Aristotle. The only indication of the chemical composition of bodies external to the earth was obtained from meteorites. It was, indeed, noted with interest that meteorites contained no elements except those which were already known to exist on the earth. The origin of meteorites was, however, at that time too obscure to enable any sound inference to be drawn about the composition of the celestial bodies generally. Indeed it might have been urged with much force that as the meteorites had been falling on the earth for countless ages an appreciable proportion of the materials on the earth's surface may have been accumulated from this source, so that the meteoric elements must be already discoverable in the list of terrestrial substances. In fact, we knew absolutely nothing about the composition of the globes external to the earth, and any information that was forthcoming on this subject was thus presented in the light of a revelation.

I do not here attempt to give any historical account of the discoveries. My only object is to indicate the position which Sir W. Huggins occupies, so as to comment on the address which he so fitly delivered at Cardiff. It is natural in this connection to refer to the lecture which Huggins delivered at Nottingham before the British Association in 1866, On that occasion, as some of