On the 13th of _August_ 1596, _David Fabricius_ observed the _Stella Mira_, or wonderful Star, in the _Neck_ of the _Whale_; which has been since found to appear and disappear periodically, seven times in six years, continuing in its greatest lustre for 15 days together; and is never quite extinguished. In the year 1600, _William Jansenius_ discovered a changeable Star in the _Neck_ of the _Swan_; which, in time became so small as to be thought to disappear entirely, till the years 1657, 1658, and 1659, when it recovered its former lustre and magnitude; but soon decayed, and is now of the smallest size. In the year 1604 _Kepler_ and several of his friends saw a new Star near the heel of the right foot of _Serpentarius_, so bright and sparkling that it exceeded any thing they had ever seen before; and took notice that it was every moment changing into some of the colours of the rainbow, except when it was near the horizon, at which time it was generally white. It surpassed _Jupiter_ in magnitude, which was near it all the month of _October_, but easily distinguished from it by a steady light. It disappeared between _October_ 1605 and the _February_ following, and has not been seen since that time. In the year 1670, _July_ 15, _Hevelius_ discovered a new Star, which in _October_ was so decayed as to be scarce perceptible. In _April_ following it regained its lustre, but wholly disappeared in _August_. In _March_ 1672 it was seen again, but very small; and has not been visible since. In the year 1686 a new Star was discovered by _Kirch_, which returns periodically in 404 days. In the year 1672, _Cassini_ saw a Star in the _Neck_ of the Bull, which he thought was not visible in _Tycho_’s time; nor when _Bayer_ made his Figures. [Sidenote: Cannot be Comets.] 404. Many Stars, besides those above-mentioned, have been observed to change their magnitudes: and as none of them could ever be perceived to have tails, ’tis plain they could not be Comets; especially as they had no parallax, even when largest and brightest. It would seem that the periodical Stars have vast clusters of dark spots, and very slow rotations on their Axis; by which means, they must disappear when the side covered with spots is turned towards us. And as for those which break out all of a sudden with such lustre, ’tis by no means improbable that they are Suns whose Fuel is almost spent, and again supplied by some of their Comets falling upon them, and occasioning an uncommon blaze and splendor for some time: which indeed appears to be the greatest use of the cometary part of any system[86]. [Sidenote: Some Stars change their Places.]