on the periodical Star in Collo Ceti. 743 
the meafure too little when I took it, but could not fuc- 
eeed better. 
Feb.' 7, 1780, The periodical ftar was invifible to the 
naked eye. I was but little prepared to look a long time 
for it with the telefcope ; but fuppofe I fhall be able to 
find it another time. 
maupertuis accounts for the periodical appearances 
of changeable ftars, by fuppofing that they may be of a 
flat form, like Saturn’s ring, which becomes invifible 
when the edge is pre tented to us. • 
As the periodical ftar in collo ceti appeared always 
full and round when I viewed it with a telefcope, this 
1 
might at fir ft appear to contradict the fuppofition of 
maupertuis; but, upon proper confideration, will be 
found not to be at all againft it : for, fuppofe the real ap- 
parent diameter of this fi$r to be one-third of a degree ; 
then, fince it appeared to me (I did not meafure it) at 
leaft of one fecond, when at the full, it will follow, that 
there was an aberration whatever might be the caufe of 
it, which amounted to 59'", by which its real apparent 
diameter was increafed from 1"' to 1". Now, if this ftar, 
in one certain pofition, fliould prefent its circular difk of 
j w in diameter, and in another fituation only its flat 
edge which would appear as a line of in length, both 
appearances, with the aberration included will ftill 
remain 
