329 
 XLIV. 
METHOD OF DISPLAYING AT ONE VIEW ALL THE ANNUAL 
CYCLES OF THE EQUATION OF TIME, IN A COMPLETE 
REVOLUTION OF THE SUN’S APOGEE. 
BY JAMES DEAN, a.m. A. 4.5. 
Prof. Math. and Nat. Phil. in the University of Vermont, 
Communicated in a letter to Nathaniel Bowditch, a.m. a. A. S. 
— <5 
FROM my first understanding the difference between mean and 
apparent time, I particularly wished to see the effect of differently com- 
bining the causes which produce it. But I could not. think of com- 
puting a whole table for every longitude of the sun’s apogee; nor even 
if that were done, would they exhibit the constituent parts or the 
transition from one table to another, The accompanying draught in 
some measure answers my purpose, and has given me.some new views 
of the subject. The construction of the curves will naturally suggest 
the manner of their operation. After drawing and properly graduating 
the ecliptic, the circle of the year, and that for the revolution of the 
sun’s apogee, a slender circle of 4 inches diameter was drawn for a 
‘standard of mean time. From this circle was set off at the distance 
of every 5° the reduction of the ecliptic to the equator, converted into 
time on a scale of 30’ to an inch, on the outside of the circle when it is 
positive, and on the inside when it is negative, and these points con- 
nected by acurve. The situation of any point in this curve compar- 
ed with the circle evidently shows that part of the equation of time 
which arises from the obliquity of the earth’s axis, for the day against 
which it is taken. On the moveable paper was drawn an sgostcrcte 
for the panne porpose with the other, and a line drawn through it 
