Professor Gautier on the Comet of July 1825. 809 
only be seen from Geneva a portion of its tail above the moun- 
tain of Saleve, the head and nucleus remaining concealed behind 
the mountain. It is to the inhabitants of the southern countries 
that the advantage will probably be reserved of seeing this co- 
met at the period in which, from its being then nearest the sun, 
its tail must be longest. On the 10th December, at the moment 
of its passing the perihelion, its heliocentric latitude will be 
about 82° 25', its distance from the earth Pp 1.85, or nearly six- 
ty-four millions of leagues; its southern declination about 42° 8P; 
and its right ascension 290° 25' ; so that it will be then situated 
in the southern part of the constellation of Sagittarius. Its 
elongation, or its angular distance from the sun, seen from the 
earth, which, at this moment, will be 67° 20', will afterwards 
tend to diminish rapidly ; and, towards the 8th January 1826, 
the comet will be found at C, in conjunction with the sun, or on 
the same side with that star, with relation to the earth C, and 
having the same longitude. The distance from the sun will be 
then 1.811, and its distance from the earth 2.207, or seventy- 
six millions of leagues. It south heliocentric latitude will be 
32° 2', and the brightness of the sun will for some time conceal 
it even from the observers above whose horizon it will pass. 
After this period, the figure shews that the comet, although 
continuing to remove from the sun, must tend anew to approach 
the earth, from the very circumstance of the opposite direction 
of their heliocentric motion. But the motion in longitude of the 
comet beginning to become slower, on account of the diminution 
in curvature of the portion of its trajectory which it then de- 
scribes, it will be the earth that must traverse the greater part of 
the arc of longitude necessary in order to its being again found on 
the same direction as the comet seen from the sun, and between 
these two stars. This will be a second opposition on the part 
of the comet, which will correspond to a point of the ecliptic al- 
most opposite to that of the first, and will take place, according 
to my calculation, towards the 8th May 1826, the comet being 
then to be found at O 7 , and the earth at o'. The distance of 
the comet from the sun will be then 2.449, and that from the 
earth only 1.453, or about fifty millions of leagues. The south 
heliocentric latitude of the comet will not be more than 7° 17', 
its southern declination will be 28° 40 7 , and its right ascension 
