The confusion thus arising is especially great in the southern hemisphere, where it has been intensified by the subdivision of one of the old con- The stellations. The ancient constellation Argo Southern covered so large a region of the heavens, Constellaand included so many conspicuous stars, that it was divided into four, representing various parts of ship—the a ship the sail, the poop, the prow, and the hull.

tions.

Dr. Gould, while director of the Cordoba Observatory, during the years 1870 to 1880, constructed the Uranometria Argentina, in which all the stars visible to the naked eye from the south pole to a parallel of declination ten degrees north of the celestial equator were catalogued and mapped. He made a revision. of the boundaries of each constellation in such a way as to introduce greater regularity. The rule generally followed was that the boundaries should, so far as possible, run in either an east-and-west or a northand-south direction on the celestial sphere. They were so drawn that the smallest possible change should be made in the notation of the conspicuous. stars; that is, the rule was that, if possible, each bright star should be in the same constellation as before. The question whether this new division shall replace the ancient one is one on which no consensus of view has yet been reached by astronomers. plicity is undoubtedly introduced by Gould's arrangement; yet, in the course of time, owing to precession, the lines on the sphere which now run north and south or east and west will no longer do so, but will

Sim

deviate almost to any extent. The only advantage then remaining will be that the bounding lines will generally be arcs of great circles.

When the heavens began to be carefully studied, two or three centuries ago, new constellations were introduced by Hevelius and other astronomers to fill the vacant spaces left by the ancient ones of Ptolemy. To some of these rather fantastic names were given; the Bull of Poniatowski, for example. Some of these new additions have been retained to the present time, but in other cases the space occupied by the proposed new constellation was filled up by extending the boundaries of the older ones.

At the present time the astronomical world, by common consent, recognises eighty-nine constellations in the entire heavens. In this enumeration Argo is not counted, but its four subdivisions are taken as separate constellations.

A glance at the heavens will make it evident that the problem of designating a star in such a way as to Naming distinguish it from all its neighbours must the Stars. be a difficult one. If such be the case with the comparatively small number of stars visible to the naked eye, how must it be with the vast number that can be seen only with the telescope? In the case of the great mass of telescopic stars we have no method of designation except by the position of the star and its magnitude; but with the brighter stars, and, indeed, with all that have been catalogued, other means of identification are available.

It is but natural to give a special name to a con

spicuous star. That this was done in very early antiquity we know by the allusion to Arcturus in the Book of Job. At least two such names, Castor and Pollux, have come down to us from classical antiquity, but most of the special names given to the stars in modern times are corruptions of certain Arabic designations. As an example we may mention Aldebaran, a corruption of Al Dabaran The Follower. There is, however, a tendency to replace these special names by a designation of the stars on a system devised by Bayer early in the seventeenth century.

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This system of naming stars is quite analogous to our system of designating persons by a family name and a Christian name. The family name of a star is that of the constellation to which it belongs. The Christian name is a letter of the Greek or Roman alphabet or a number. As any number of men in different families may have the same Christian name, so the same letter or number may be assigned to stars any number of constellations without confusion. The work of Bayer was published under the title of Uranometria, of which the first edition appeared in 1601. This work consists mainly of maps of the stars. In marking the stars with letters on the map, the rule followed seems to have been to give the brighter stars the earlier letters in the alphabet. Were this system followed absolutely, the brightest star should always be called Alpha; the next in order Beta, etc. But this is not always the case. Thus in the constellation Gemini, the brightest star is Pollux, which is marked Beta, while Alpha is the second brightest. What sys

tem, if any, Bayer adopted in detail has been a subject of discussion, but does not appear to have been satisfactorily made out. Quite likely Bayer himself did not attempt accurate observations on the brightness of the stars, but followed the indications given by Ptolemy or the Arabian astronomers. As the number of stars to be named in several constellations exceeds the number of letters in the Greek alphabet, Bayer had recourse, after the Greek alphabet was exhausted, to letters of the Roman alphabet. In this case the letter A was used as a capital, in order, doubtless, that it should not be confounded with the Greek a. In other cases small italics are used. In several catalogues since Bayer, new italic letters have been added by various astronomers. Sometimes these have met with general acceptance, and sometimes not.

Flamsteed was the first Astronomer Royal of England, and observed at Greenwich from 1666 to 1715. Among his principal works is a catalogue of stars in which the positions are given with greater accuracy than had been attained by his predecessors. He slightly altered the Bayer system by introducing numbers instead of Greek letters. This had the advantage that there was no limit to the number of stars which could be designated in each constellation. He assigned numbers to all the brighter stars in the order of their right ascension, irrespective of the letters used by Bayer. These numbers are extensively used to the present day, and will doubtless continue to be the principal designations of the stars to which they refer. It is very common in our modern catalogues

to give both the Bayer letter and the Flamsteed number in the case of Bayer stars.

The catalogues by Flamsteed do not include quite all the stars visible to the naked eye; but various uranometries have been published which were intended to include all such stars. In such cases the designations. now used frequently correspond to the numbers given in the uranometries of Bode, Argelander, and Heis.

In recent times these uranometries have been supplemented by censuses of the stars, which are intended to include all the stars to the ninth or tenth magnitude. I shall speak of these in the next section; at present it will suffice to say that stars are very generally designated by their place in such a census.

There is still here and there some confusion both as to the boundaries of the constellations and as to the names of a few of the stars in them. I have already remarked that, in drawing the imaginary boundaries on a star map, as representing the celestial sphere, different astronomers have placed the lines differently. One of the regions in which this is especially true is in the neighbourhood of the north pole, where some astronomers place stars in the constellation Cepheus which others place in Ursa Minor. Hence in the Bayer system the same star may have different names in different catalogues. Again, in extending the names or numbers, some astronomers use names which others do not regard as authoritative. The remapping of the southern hemisphere by Dr. Gould changed the boundaries of most of the southern constellations in a way already mentioned.