52 



THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



with a motion so slow that 25,868 years are re- 

 quired for a single circuit of the swaying axis 

 around an imaginary line upright to the plane in 

 which the earth travels. And we know that in 

 consequence of this reeling motion the points of 

 the heavens opposite the earth's poles necessarily 

 change. So that the southern pole, now eccen- 

 trically placed amid the region where there were no 

 constellations in old times, was once differently sit- 

 uated. But the circumstance which seems to have 

 been overlooked is this, that, by calculating back- 

 ward to the time when the southern pole was in the 

 centre of that vacant region, we have a much bet- 

 ter chance of finding the date (let us rather say the 

 century) when the older constellations were formed 

 than by any other process. We may be sure not 

 to be led very far astray, for we are not guided 

 by one constellation but by several, whereas all 

 the other indications which have been followed 

 depend on the supposed ancient position of sin- 

 gle constellations. And then most of the other 

 indications are such as might very well have be- 

 longed to periods following long after the inven- 

 tion of the constellations themselves. An as- 

 tronomer might have ascertained, for instance, 

 that the sun in spring was in some particular 

 part of the Ram or of the Fishes, and later a 

 poet like Aratus might describe that relation 

 (erroneously for his own epoch) as characteristic 

 of one or other constellation ; but who is to as. 

 sure us that the astronomer who noted the rela- 

 tion correctly may not have made his observation 

 many hundreds of years after those constellations 

 were invented ? Whereas, there was one period, 

 and only one period, when the most southern- 

 most of the old constellations could have marked 

 the limits of the region of sky visible from some 

 northern region. Thus, too, may we form some 

 idea of the latitude in which the first observers 

 lived. For in high latitudes the southernmost of 

 the old constellations would not have been visi- 

 ble at all, and in latitudes much lower than a 

 certain latitude presently to be noted these con- 

 stellations would have ridden high above the 

 southern horizon, other star-groups showing be- 

 low them which were not included among the 

 old constellations. 



I have before me, as I write, a picture of the 

 southern heavens, drawn by myself, in which this 

 vacant space — eccentric in position, but circular 

 in shape — is shown. The centre lies close by 

 the Lesser Magellanic cloud, between the stars 

 Kappa Toucani and Eta Hydri of our modern 

 map?, but much nearer to the last named. Near 

 this spot, then, we may be sure, lay the southern 



pole of the star-sphere, when the old constella- 

 tions, or at least the southern ones, were in- 

 vented ; and, if there had been astronomers in 

 the southern hemisphere, Eta Hydri would cer- 

 tainly have been their pole-star. 



Now, it is a matter of no difficulty whatever 

 to determine the epoch when the southern pole 

 of the heavens was thus placed. 1 Between 2,100 

 and 2,200 years before the Christian era, the 

 southern constellations had the position de- 

 scribed, the invisible southern pole lying at the 

 centre of the vacant space of the star-sphere — 

 or rather of the space free from constellations. 

 It is noteworthy that, for other reasons, this 

 period, or rather a definite epoch within it, is 

 indicated as that to which must be referred the 

 beginning of exact astronomy. Among others 

 must be mentioned this — that in the year 2170 

 b. c, quam proxime, the Pleiades rose to their 

 highest above the horizon at noon (or technically 

 made their noon culmination) at the spring equi- 

 nox. We can readily understand that, to minds 

 possessed with full faith in the influence of the 

 stars on the earth, this fact would have great 

 significance. The changes which are brought 

 about at that season of the year, in reality, of 

 course, because of the gradual increase in the 

 effect of the sun's rays as he rises higher and 

 higher above the celestial equator, would be at- 

 tributed, in part at least, to the remarkable star- 

 cluster coming then close by the sun on the 

 heavens, though unseen. Thus we can readily 

 understand the reference in Job to the "sweet 

 influences of the Pleiades." Again, at that same 

 time, 2170 b. c, when the sun and the Pleiades 

 opened the year (with commencing spring) to- 

 gether, the star Alpha of the Dragon, which was 

 the pole-star of the period, had that precise posi- 

 tion with respect to the true pole of the heavens 

 which is indicated by the slope of the long pas- 

 sage extending downward aslant from the north- 

 ern face of the Great Pyramid ; that is to say, 

 when due north below r the pole (or at what is 

 technically called its sub-polar meridional pas- 

 sage), the pole-star of the period shone directly 

 down that long passage, and I doubt not could 

 be seen not only when it came to that position 

 during the night, but also when it came there 

 during the daytime. 



But some other singular relations are to be 



1 It is. by-the-way, somewhat amusing to find Baron 

 Humboldt referring a question of this sort to the great 

 mathematician Gauss, and describing the problem as 

 though it involved the most profound calculations. Ten 

 minutes should suffice to deal with any problem of the 

 kind. 





