c 1 66 3 
IX. On the Method of observing the Changes that happen to the 
fixed Stars ; with some Remarks on the Stability of the Light 
of our Sun. To which is added, a Catalogue of comparative 
Brightness, for ascertaining the Permanency of the Lustre of 
Stars. By William Herschel, LL. D. F. R. S. 
Read February 25, 1 796. 
T he earliest observers of the stars have taken notice of their 
different degrees of brilliancy, and, by way of expressing their 
ideas to others, have classed them into magnitudes. Bright- 
ness and size among the stars were taken as synonymous 
terms, and may still be used as such with sufficient truth, 
notwithstanding the latter, it seems, can only be looked upon 
as the consequence of the former. The brightest stars were 
called of the first magnitude ; the next of the second ; and 
those of an inferior lustre of the third, fourth, and fifth mag- 
nitudes ; and so on. 
Among the stars of the first two or three classes there 
seems to be some natural limit which confines them to a par- 
ticular order. If we suppose the stars to be about the size of 
our sun, and at nearly an equal distance from us and from 
each other, those which form the first inclosure about us will 
appear brighter than the rest, and there can be only a small 
number of them. This hypothesis is nearly confirmed by 
observation, as may be seen by looking over a globe, and 
applying a pair of compasses opened to 60 degrees, which 
