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Rh very low temperatures, and hence the wide range through which life is possible.

The next station is Uranus, but the interval between is vast. The stage from the one orbit to that of the other is about one-third of the whole journey to the sun. In a railway train, running at the ordinary speed, this distance could not be done under less than six thousand years; so that, if the train started at the creation of man, it would not have yet reached this first station on the way to the sun. The planets, however, are closer as you approach the sun, just as on a railway the stations become more numerous as you approach the metropolis. In our cometary vehicle, the speed is always increasing, so that, although slow as a railway train at first, it soon acquires immensely greater speed as it rushes on towards its distant goal. The comet of Halley, though starting so far beyond the verge of the system, takes only about forty years to reach the sun. The railway train, going always at the same rate, would take 10,000 years from the remotest orbit of the system to the centre.

With our increased velocity, Uranus has less influence in drawing us out of our course. Here we find numerous satellites. Sir William Herschel discovered six, but only four have been detected by others. It is, however, highly probable that the number is greater even than that assigned by