6‘o 
Dr. Herschei/s Observations on the 
are placed in the reverse order of the rotation, that the calcu- 
lated motion of the belt may immediately point out the place 
which is come to the meridian. Thus, if the point K at 180 
has moved 53 degrees forward, the situation x, on the belt, 
may be concluded to be on the meridian ; because it is at 
180 -f 53, that is, the 233d degree. 
Assuming for an epoch the observation of Dec. 4. 4 h 57', 
where the different small belts, that make up the quintuple 
belt, are described as quite uniform ; let it be placed at the 
180th degree of the divided circle, where it will be fully ex- 
posed to the view of the observer. 
I now select a few observations that are strongly marked, 
and as far distant from each other as can be found, by way of 
trying in what rotation they will agree. Such are the follow- 
ing two : Dec. 4. 6 h 52' ; Jan. 7. 3 h 44', for the places where 
the belts were uniform ; and other two, Dec. 6. y h 52', 
Jan. 4. 2 h 35', for places where they appeared unequal. The 
sidereal times being corrected, and brought to true mean time, 
we have from Dec. 4. i3 h 46' 51", to Jan. 7. 8 h 25' 11" an in- 
terval of 33 days i8 h 38' 20" ; in which time let us suppose 79 
revolutions to have been made. This will give io h 15' 40" 
for the time of each revolution. 
In the next place, we have from Dec. 6. i4 h 38'47" to Jan. 4. 
7* 28' 12" an interval of 28 days i6 h 49' 25"; and allotting 67 
revolutions to this, we obtain io h 16' 51" for the time of the 
rotation. These periods being independent of each other, and 
the observations having been made upon different parts of the 
belt, agree very well together. But now, some intermediate 
places are wanted, by way of trying, whether the period thus 
determined will accord with the rest of the observations ; and 
