CHAPTER I.
THE MOVEMENTS OF THE SOLAR SYSTEM.
HAVE often speculated as to the appearance which the heavens must have presented at very remote epochs. I do not now merely refer to such epochs as those to which human history extends. There can be no great difference between the aspect of the skies now and the aspect which they presented when Ptolemy or Hipparchus observed them. No doubt we must admit that some changes have taken place, for change is the law of nature. In a thousand years, or in a hundred years, or ten years, or even in one year, a number of alterations take place in the positions of the fixed stars which are quite perceptible to the refined measurements of the modern observatory, though they would not suffice to produce a derangement of the heavens large enough to be discernible by unassisted observation. But in the present chapter I specially want to consider the variations in the aspect of the heavens, which would be presented not merely after the lapse of a few centuries or a few tens of centuries, but after
