Now referring to our figure, we find that about 1300 B.C. the two stars, [Greek: b] Ursae Minoris and [Greek: k] Draconis were fairly near the pole, and this fact leads us to date the invention of this sphere at about this epoch, rather than a little before or a little after, although, of course, there is nothing in _this_ argument (though there may be in others), to prevent us dating it when [Greek: a] Draconis was near the pole, 2850 B.C. This star was indeed said by the Chinese astronomers in the reign of Hoangti to mark the pole, which gives a date to their observations. The chief use of this latter method is to _confirm_ our conclusions from the former, rather than to originate any. Let us now apply our knowledge to the facts. In the first place we may notice that in the time of Hipparchus the vernal equinox was in the first degree of the Ram, from which our own arrangement has originated. Hipparchus lived 128 years B.C., or nearly 2,000 years ago, at which time the equinox was exactly at [Greek: b] Aries. Secondly, there are many reasons for believing that at the time of the invention of the zodiac, indeed in the first dawning of astronomy, the Bull was the first sign into which the sun entered at the vernal equinox. Now it takes 2,156 years to retrograde through a sign, and therefore the Bull might occupy this position any time between 2400 and 4456 B.C., and any nearer approximation must depend on our ability to fix on any particular _part_ of the constellation as the original equinoctial point. We may say that whoever invented the zodiac would no doubt make this point the _beginning_ of a sign, and therefore date its invention 2400 B.C.; or on the other hand, if it can be proved that the constellations were known and observed before this, we may have to put back the date to near the end of the sign, and make its last remarkable stars the equinoctial ones, say those in the horns of Taurus. Compare the line of Virgil, "Candidus auratis aperit cum cornibus annum Taurus." The date in this case would be about 4500 B.C.--or once more some remarkable part of the constellation may give proof that its appearance with the sun commenced the year--and our date would be intermediate between these two. In fact, the remarkable group of stars known as the _Pleiades_ actually does play this part. So much interest clusters, however, round this group, so much light is thrown by it on the past history of astronomical ideas--and so much new information has recently been obtained about it--that it requires a chapter to itself, and we shall therefore pass over its discussion here. Let us now review some of the indications that some part of the constellation of the Bull was originally the first sign of the zodiac.