83 
parent equinox of the date. The coefficients of d after log a, 
&e., have for unit the seventh decimal place. The obliquity 
of the ecliptic has been assumed invariable, and equal to 
23° 27’ 346. 
“¢ Tt appeared to us that the diminution of the comet’s light 
was much more rapid than theory would indicate. On March 
30, it shone as a good second magnitude star; on April 15 
certainly not more than ninth; at least, such was Mr. Cooper’s 
impression* as well as my own. A comparison of the distances 
from the earth and sun, at these two dates, gives the light on 
April 15, 6-4 times less than that on March 30, which would 
be perhaps equal to that of a star of fifth or sixth magni- 
tude. Iam not aware that this circumstance has been no- 
ticed with regard to the present comet, and therefore venture 
to direct attention to it as having an important bearing on 
the physical theory of these remarkable bodies. 
*¢ One is still disposed to sift the probability ofa collision 
with the earth or one of her sister planets. Weare certainly 
out of harm’s way so far as this comet isconcerned. It wasin 
ascending node on March 1, at 22> 13™, astronomical mean 
time at Greenwich. Distance from the sun, 66,193,000 miles ; 
therefore, 3,259,000 miles within the orbit of Venus. It was 
then nearly 157 millions of miles from us. It was in descend- 
ing node April 44 22" 46™. Distance from the sun, 43,973,000 
miles; nearly 12 millions of miles without the orbit of Mer- 
cury. It was then nearly 83 millions of miles distance from 
the earth. The comet was in perigee April 1‘ 8"; distance, 
80,600,000 miles. 
‘‘The only thing worthy of notice, with regard to the 
computations, is, that in correcting the elements Laplace’s 
method failed. The cause is easily explained. For the mid- 
dle time the angle at the comet, formed by lines drawn to the 
* Such, Sir W. R. Hamilton stated, was also the impression of his Assis- 
tant, Mr. Charles Thompson, and his own, on the evening above referred to. 
