66 Dr. Herschel’s Observations, &c. 
Last of all, the place y, being truly pointed out by computa- 
tion for Jan. 1 6, after a series of an hundred revolutions since 
the 4th of December, must concur in supporting our assigned 
period. 
I shall only add one general remark, which is, that if we 
lengthen the time of the rotation but 2 minutes, it will throw 
the last observation back above 116 degrees; and if we dimi- 
nish it by 2 minutes, there will arise an excess of more than 
117; and, in either case, the calculations and observations 
would be totally at variance : from which we may conclude 
that our period must be exact to much less than 2 minutes, 
either way. Indeed, what alterations may have taken place 
in the belts themselves, it is impossible to determine. That 
there have been some, we may admit, and rather suppose, but 
we have no particular reason to suspect them to have been 
very considerable. And, after we have shewn that a proper 
motion, in the spots of the belts, of 1 16 degrees one way, or 
of 117 the other, would only occasion an error of 2 minutes 
in time, we need not hesitate to fix the rotation of the planet 
Saturn upon its axis at io h 16' o",*. 
Slough, near Windsor, WM. HERSCHEL. 
Jan. 22, 1794. 
Erratum. Phil. Trans, for 1793. Part II. page 215. 2d line, for more than two degrees 
and a third, read i°u' 47",6. 
