Now the question whether any real resemblance attracted the attention of the earlier observers in such cases as this is by no means without interest. If such a resemblance formerly existed, and does not now exist, it would follow that quite a considerable proportion of the stars have changed in brightness. Considering that each star is a sun, the centre, most probably, of a system like that which circles around our own sun, such a conclusion would be very startling indeed. It would have a special interest for ourselves, somewhat in the same way that the news that many railway accidents occur has an interest for those who travel much by rail. If accidents frequently happen to those other suns, in such sort that they either lose or gain greatly in brightness, an accident of one or other kind might well happen to our own sun, in which case the inhabitants of this earth would perish. For many of the stars, by our supposition, would have changed so much as either to lose their character as the defining stars of a constellation or by accession of brightness to acquire that character which in old times they had not possessed. Now, assuredly, a change of brightness competent to affect _our_ sun's character (as viewed from any remote star system) in equal degree, would be destructive to the inhabitants of the earth. None at least of the higher races of animals or plants could bear the intense cold resulting from a change of the former kind, or the intense heat resulting from a change of the latter kind. Yet, if the constellations were once named because of their imagined resemblance to various objects, and if no such resemblance can now be even imagined, a change of one or other kind in the condition of our sun must be regarded as probable,--much in the same way that a regular traveller by train on any line must be regarded as exposed to danger, if accidents are known to be continually happening on that line.
What I now propose to do is to inquire whether we may not find the true figures and proportions of the ancient constellations in another way--viz., not by looking for them among the constellations as at present bounded and figured in our star-maps, but by searching the heavens themselves for them. This general method of search occurred to me very long ago while I was preparing various star-atlases, but the special mode of illustration here adopted occurred to me lately, while preparing for young astronomers in the United States a series of monthly maps showing the skies towards the north, south, east, and west, at different times of the night all the year round, and in various latitudes within the limits of the States. When I was in America I noticed, as I travelled about over a tolerably wide range of latitude, that the varying attitudes assumed by several of the constellations suggested features of resemblance to different objects. In constructing maps, simple in appearance, but based in reality on careful calculations, this characteristic came out more clearly. Adopting a particular way of presenting the connection between the various stars of a constellation, I often found the figure suggested which had actually been associated with the group of stars thus connected. Lastly, the idea of extending this method to other cases naturally occurred to me, and some of the results are presented in the present essay.