308 Professor Gautier on the Comet of July 1825. 
distance from the earth d, of nearly three times that quantity, 
or of more than a hundred millions of leagues. It was then at 
an elevation of about 26° above the equator ; and was in the 
part of its orbit situated above the ecliptic. But it advanced 
rapidly toward this plane^ approaching the descending node N, 
which it attained on the 23d August, about 11 o'clock in the 
evening. Its motion in longitude being in the contrary direc- 
tion to that of the earth, the two stars then tended by this cir- 
cumstance to approach each other rapidly, although the comet 
must have appeared to remain nearly in the same position with 
relation to the earth as is shewn by the figure. After the two 
bodies had been much approximated, the geocentric motion 
of the comet must have become more rapid, and its brightness 
less apparent. Towards the 9th October at noon, the comet was 
in O, and the earth in o; the first being in opposition to the 
sun in longitude, or situated on the side opposite the sun with 
relation to the earth, and having already descended, relatively to 
this latter, about 33° 10' beneath the ecliptic. It was then that the 
comet and the earth were nearest one another ; and, I find that 
their distance at this period was not more than 0.615 of that of 
the earth from the sun, or about twenty-one millions and a quar- 
ter of leagues. The tail, at this period, had an apparent length 
of about 12°, although it was then visible to us only as shorten- 
ed in a very high degree ; at least it would be so, were we to 
suppose it having a direction contrary to the earth, and directly 
opposite to the sun, as they ordinarily have. On this supposition 
we should find, that its real length must have been more than 
eight millions of leagues. M. Pons remarked at that time in it 
(Corr. Astr. t. xiii. p. 394.) three very distinct rays at equal 
distances from one another, and of unequal length, present- 
ing some resemblance to the rays of the comet of 1144, such as 
they have been described by the astronomer de Loys de Che- 
seaux of Lausanne, in his treatise on that comet. 
After this the comet began to remove from the earth, in con- 
sequence of the contrary motion of the two bodies, and it was, 
in fact, remarked, on the latter days of its appearance, that the 
tail already appeared less brilliant. The comet continuing to 
descend beneath the ecliptic, quickly disappeared from our 
view in consequence ; and, on the 18th October, there could 
