174 _ W. A. Norton—Coggia’s Comet. 
form the following side. The time required for any receding 
particle receiving an initial velocity in the line of direction of 
the sun, to reach its point of greatest recess, must have been 
less than twenty-four hours, in the cage of the two comets 
(Donati’s and Coggia’s) for which the intensity of the actual 
solar repulsion has been determined. 
Let nes gq (Fig. 3) represent the nucleus, or more strictly the 
surface of projectile discharge, and n’e’ s’q’ the sphere of sen- 
sible action of the nucleus ; e g being the equator and ce R the 
direction of the sun. The point p is at lat. 35°, and ris the 
point of projection of the jet which issues from the sphere 
n’e’ s'q’ in the direction 7’ A parallel toce R. The jets pro- 
ceeding from the are er issue from this sphere at various 
points from u to 7’. One of these jets proceeding from a certain 
point near e will have at v a direction at right angles to ce R, 
+ 
If the jet discliarge extend beyond r to some point z the jet 
proceeding from z will emerge trom the sphere n 
erge 
the same sphere between 7’ and z’. Now letn’e’s' 7 (Fig. 4) 
any jet emerging from this sphere to the line n’cs' perpendic- 
ular to the radius vector ce’ &. Sup a Cosiated from 
