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 mass of Jupiter, and yet no one will, on that account, claim that meteorites have been derived from that planet.

The identity of the actual materials in the varied bodies of the solar system is so striking, that it would now seem wonderful if any object which undoubtedly belonged to that system contained materials to any considerable extent not otherwise known to us from their presence in the earth. It appears that there is, therefore, no force in the argument which would connect meteorites with comets, merely because iron and some other substances have been found common to both. On the other hand, the very form in which the iron is found in meteorites, and the condition in which iron must exist in bodies possessing the nature of comets, seems to afford conclusive evidence that the origin of meteorites, and the origin of comets, must be sought for in widely different directions.

Everything we know with regard to the structure or texture of a comet, seems to demonstrate that it is not in the least likely to contain solid masses of which meteorites might be fragments. Take, for instance, the ordinary telescopic comet of which some half-dozen or so come to visit our system every year. Such a body is a light volume of gas or vapour far less dense than the lightest cloud that ever floated in a summer sky. Indeed, it is well known that, as such a comet in its progress across the heavens passes between us and the stars, those stars are often seen twinkling brilliantly right through the many thousands of miles of cometary matter, which their rays have to traverse, The lightest haze in our atmosphere would suffice to extinguish the faint