shooting-stars. Whatever may be the nature of the belief entertained with regard to comets in other respects, it seems quite impossible to regard these bodies as composed of materials in anything like the same forms as those which we find in a meteorite. No doubt the mere elements present in comets may be much v the same as those from which meteorites are constituted. In illustration of this I need not do more than refer to the single element iron. It seems to have been demonstrated that iron is a constituent of certain great comets. This same element is of course a leading component of meteorites, and it might therefore be contended that to this extent there was an affinity between the two different classes of bodies. It may also be added that sodium has been found both in comets and in meteorites, while a still more striking instance is presented in the case of the element carbon. This remarkable substance often seems to be one of the principal constituents in a comet, in so far at least as the spectra of those bodies may be regarded as indications of the proportions in which the different elements have united to form it. A curious discovery with regard to the composition of meteorites has been the detection of graphite, as well as of carbon in other forms. Indeed, it may be noted as an interesting circumstance that M. Moisson, in his recent investigations of a meteorite from the Canon Diablo, detected the presence of minute particles of carbon which possessed the hardness of diamonds.
But while we admit all this it seems that the evidence on the other side is far too strong to permit us to regard comets, and meteorites, as derived from the same source, or as standing to each other in any particular relation. It would be easy to over-estimate the significance of
