56 H. A. Newton on November Star-Showers. : ; 
the last column of the table shows no regularity. On the con- 
trary, while the sum of the maxima of all the plus perturbations 
of the radius vector is 884, and that of the minus perturbations 
is 958, we have two remarkable showers occurring, one in A. 
1202, when the increase was 622, and one in A. D. 1366, when 
the decrease was 621. If then a uniform ring, crossing the 
ecliptic just inside or just outside of the earth’s orbit, be su 
, the cause of the periodicity cannot be the perturbations 
of the earth’s radius vector. The greatest possible perturbation 
in either direction being only about 9000 miles, it is highly im- 
probable that the earth passes sometimes inside and sometimes 
outside of a thin ring. 
We might however suppose that the ring sways back and _ 
forth, and thus produces the periodicity. The mean motion of 
the bodies of the ring and its eccentricity are unknown, and | 
hence we cannot speak positively of its irregularities. But it is 
probable that its radius vector would not suffer larger perturba- 
tions than that of the earth. The lunar action is wanting, while 
the earth ought to work the same effect each year. The motion 
. 
is retrograde, as will be shown, hence the action of the planets 
Bee, Seco bers of 
stragais 
