176 _ W. A. Norton—Coggia’s Comet. 
In Fig. 5 the solar repulsion is assumed to be inversely pro- 
portional to sin 6. The change of direction of the jet while 
passing through the sphere of sensible action of the nucleus is 
neglected in the application of this law. Two systems of 
curvilinear jets are shown—one answering to values of a varying 
by 10° from 50° to 90°, and emanating from latitudes less than 
35° of the right hemisphere, or from a portion of the arc er 
(Fig. 3); and another answering to values of a varying by 10° 
from 90° to 180°, and estimated from right to left. These em- 
anated from latitudes greater than 35° of the left hemisphere, 
or from a portion of the are r, x (Fig. 8’. The other corres- 
ponding systems of jets, emanating from portions of er, and r 2, 
would form the other half of the comet. If we consider all 
the jets issuing from the right hemisphere as forming one sys- 
tem, and all those issuing from the left hemisphere as forming 
another system, then for each system a will vary from 50° to 
180°: and will increase from left to right for the first, and from 
right to left for the second. They answer to the supposition 
that the outstreaming extends from latitude 174° to 574°, in 
each hemisphere. It will be seen that the jets proceeding 
from the latitudes higher than 35°, for which a varies from 90° 
to 180°, recede to greater distances from the nucleus than those 
emanating from latitudes less than 35°, for which a varies from 
50° to 90°. This of course results from the greater values of 
sin 6 that obtain for the first-mentioned set of jets. Thus, for 
the 130° jet sin 6=0-953, while for the 50° jet sin 6=0534. 
_ The envelope, Vaéd, or outer boundary of the latter system of 
jets thus falls within that, Va’ d’ a’, of the other system. The 
overlapping of the two systems of jets should accordingly be 
conspicuously visible, and an appearance presented similar to 
at of Coggia’s comet on July 12th, as shown in the drawing 
on page 165. 
Certain comets have presented peculiarities of appearance which 
I find, on a careful examination, admit of pisisdocsoty explanation 
on the hypothesis that the equator of the nucleus was inclined to 
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