Chapter 60. On the distinction between _stella_, _sidus_, and _astrum_. 1. _Stellae_, _sidera_, and _astra_ differ from one another. For _stella_ is any separate star. _Sidera_ are made of very many stars, as Hyades, Pleiades. _Astra_ are large stars as Orion, Bootes. But the writers confuse these names, putting _astra_ for _stella_ and _stella_ for _sidera_.[273] [273] Isidore does not observe the distinctions he lays down here. He does not seem to have known that Orion and Bootes were constellations. Chapter 61. On the light of the stars. 1. Stars are said to have no light of their own, but to be lighted by the sun like the moon. Chapter 62. On the position of the stars. 1. Stars are motionless, and being fixed are carried along by the heavens in perpetual course, and they do not set by day but are obscured by the brilliance of the sun. Chapter 63. On the courses of the stars. 1. Stars either are borne along or have motion. Those are borne along which are fixed in the heavens and revolve with the heavens. Certain have motion, like the planets, that is, the wandering stars, which go through roaming courses, but with definite limitations. Chapter 64. On the varying courses of the stars. 1. According as stars are carried on different orbits of the heavenly planets, certain ones rise earlier and set later, and certain rising later come to their setting earlier. Others rise together and do not set at the same time. But all in their own time revolve in a course of their own. Chapter 65. On the distances of the stars. 1. Stars are at different distances from the earth and therefore, being of unequal brightness, they are more or less plain to the sight; many are larger than the bright ones which we see, but being further away they appear small to us. Chapter 66. On the circular number of the stars. 1. There is a circular number of the stars by which it is said to be known in what time each and every star finishes its orbit, whether in longitude or latitude.[274] [274] Du Breul has in addition: _latitudo intelligitur per signiferum, longitudo per proprium excursum_. 2. For the moon is said to complete its orbit in eight years, Mercury in twenty, Lucifer in nine, the sun in nineteen, Pyrois in fifteen, Phaeton in twelve, Saturn in thirty. When these are finished, they return to a repetition of their orbits through the same constellations and regions. 3. Certain stars being hindered by the rays of the sun become irregular, either retrograde or stationary, as the poet relates, saying: Sol tempora dividit aevi Mutat nocte diem, radiisque potentibus astra Ire vetat, cursusque vagos statione moratur. Chapter 67. On the wandering stars. 1. Certain stars are called _planetae_, that is, wandering, because they hasten around through the whole universe with varying motions.... Chapter 68.