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 whatever argument may be derived from the similarity in ultimate chemical composition. It must be remembered that one of the most remarkable results of spectroscopic analysis has been to suggest the practical identity as to ultimate composition of the different bodies of the solar system. There is no good reason to believe, so far as spectroscopic evidence is concerned, that there are any considerable number of elements present in the sun, in addition to those elementary bodies with which terrestrial chemistry has made us acquainted. There is no doubt a mysterious indication of some possible element of an extremely light description in the solar corona, for which the name of "coronium" has been suggested; and there is also some element known as "helium" which is believed to be found in the prominences. But the existence of the bodies so designated is still undemonstrated; and even if it were, the presence of the bodies of such a character would not affect our present argument.

It is therefore not surprising that the elementary bodies which have been discovered in the meteorites should resemble those already known on the earth. Nor need it be a matter for astonishment if the materials found in comets should resemble those found elsewhere throughout the solar system. I therefore think that we are warranted in refusing to draw any inference from the fact that iron is present, both in some meteorites and in some comets, with reference to the presumed relationship between these two classes of celestial objects. They both have iron and carbon simply because they both belong to the solar system, where iron and carbon are elements which appear to be widely distributed. No one will be likely to doubt that iron and carbon are both present in