Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 2.djvu/434

386 and ſcarcely inferior to Venus in ſplendor. Tycho Brahe ſaw it upon the 11th of the ſame month when it ſhone with the greateſt luſtre; and from that time he obſerv'd it to decay by little and little; and in 16 months time it entirely diſappear'd. In the month of November, when it firſt appeared, its light was equal to that of Venus. In the month of December its light was a little diminiſhed, and was now become equal to that of Jupiter. In January 1573. it was leſs than Jupiter and greater than Sirius, and about the end of February and the beginning of March became equal to that Star. In the months of April and May it was equal to a Star of the 2d magnitude. In June, July and Auguſt to a Star of the 3d magnitude. In September, October and November to thoſe of the 4th magnitude, in December and January 1574. to thoſe of the 5th, in February to thoſe of the 6th magnitude, and in March it entirely vaniſhed. Its colour at the beginning was clear, bright and inclining to white, afterwards it turned a little yellow, and in March 1573. it became ruddy like Mars or Aldebaran; in May it turned to a kind of dusky whiteneſs like that wee obſerce in Saturn, and that colour it retained ever after, but growing always more and more obſcure. Such alſo was the Star in the right foot of Serpentarius, which Kepler's ſcholars firſt obſerved September 30. O.S. 1604. with a light exceeding that of Jupiter, tho' the night before it was not to be ſeen. And from that time it decreas'd by little and little, and in 15 or 16 months entirely diſappeared. Such a new Star, appearing with an unuſual ſplendor, is ſaid to have moved Hipparchus to obſerve, and make a catalogue of, the fixed Stars. As to thoſe fixed Stars that appear and diſappear by turns, and encreaſe ſlowly and by degrees, and ſcarce ever exceed the Stars of the 3d magnitude, they ſeem to be of another kind, which revolve about their axes, and having a light and a dark ſide, ſhew thoſe two