94 W. A. Norton on Comets. 
hand the pote which are emitted from the sides of the nucle 
er small angles, (a), are iter moving with m 
creasing velocity, and hence, those which follow each other, 1 
A still greater deviation from the Brie. age form would result 
will be expressed by ae xX sin a, or & On this hypothess | 
the form of the head would be nearly circular. The a . 
form has in fact often been observed (e. g. the semi-circular zr . 
or hood, resting upon the nucleus of Donati’s comet, ae : 
ee passage; also head of Halley’s comet, on Oct. fh 
If we adopt the idea that the nucleus exercises no repulsif : 
action; or that its repulsion, if any, is exceeded kw attract 
_ equ. (12), shows that the form of the head must still be parabolis 
i. ae ates g to the subsequent theory of the sun’s electric action the velosity 
emission sho in general, be least at the ile i the nucleus. I conceive a 
that the repulsion should be least effective, as compared with the attraction, a 
