Gis 
Paris, and Citizen Mechain has haftily 
calculated the following elements :— 
sin 20 
Inclination of the orbit s Oo 25 
Nodes és ‘ wee Bi.'8 
Perihelion . A : E 6°77 
Diitance 3 O.- 2"%3 
Pailage, 7th of Augutt, ts hours: 
This little comet, difcovered nearly at 
the fame time by four’ different perfons, 
proves that the obfervation of comets is no 
very difhcult tafk: three or four have 
fometimes been feen in the {pace of a yeas 
and if the friends to this {cience would 
engage in the bufinefs, it is probable that 
the number would be rapidly incvreaied. 
This is what is moft wanted in aftrono- 
mical purfuits; itis mortifying, that, at 
prefent, we know not whether we are to 
reckon comets by hundreds or by thou- 
fands ;—whether they return, or are loft 
in the immenfity of the univerfe. 
A telefcope of very fimple contruction 
is only neceflary for the difcovery of 
comets, and for affigning their proper 
places and fituation to aftronomers. A 
wooden quadrant of two feet radius, 
which may be made by a common joiner, 
properly fitted up and divided, is allo necef- 
fary ; this inftrument direéted to tke place 
in which a comet is, will inftantly thew 
its height and diftance from the meridian 
atthe time of obfervation. ‘Nothing more 
is wanted by aftronomers, to find out a 
cometto which their attention has been 
called. By this method, the knowledge 
of the ftars is. not neceflary for the dilco- 
very of correts ; ; but there are a hundred 
nebulz, which, in fome refpeéts, refem- 
ble fmall comets : if, therefore, we would 
diftinguifh them, recourfe muf&t be had 
toa celeftial atlas, on which they are all 
marked :—one may be had at Paris of La- 
marche, rue du Foin. ‘This ftudy will be 
neither long nor dificult. ‘The Berlin 
atlas is much mere complete, of which we 
fall fpeak particularly hereafter. 
The telefcope made ufe of by Citizen 
Meffier, with which he has already difco- 
vered twenty comets, is two feet long, 
with an opening of 23 inches. and three 
eye-glafles: the focus of that next the eye, 
is 2% inches and zo lines opening ; the 
fecond 9, and the third 94 inches. There 
is a diftance of 10 lines between thefe twa, 
and five inches between the firft and fecond. 
This telefcope magnifies the abject but five 
times, but the field of vifion is four = 
grees. One of this kind may be had f 
about 79 or 80 francs. 
Burckhardt has alfo calculated the orbits 
of the comets which were feen, in 1763, 
The Hiftory of Afronomy, by C. Lalande. 
. ’ 
[April 1, 
1771, 1773: he found that the orbit of 
the fecond was an hyperbolic curve. 
The comet that Citizen Meflier difco- 
vered the 14th of June, 1770, ean which 
Citizen Burckhardt has made long and 
learned calculations, appears to have had 
an orbit almoft circular, and that its pe- 
riedical revolution was five years and feven- 
months. NeverthelefS this cemet has 
never been feen either before or fince the 
year 1770, which can only be attributed 
to fome great change having taken place i in 
its orbit. 
Muft we then confefs, after having 
maintained during the eighteenth century 
that all comets return after certain perio- 
dical revolutions, in the nineteenth, that, 
excepting the one feen in 1759, they do 
not revolve. Jt appears to me, that al- 
mof every thing dependsoncomets. ‘The 
only thing that I recommend to my cor- 
re{fpondents,is to look after, and attend to, 
comets ; the knowledge of comets is that 
which is alone wanting to complete the 
{cience of aftronomy. 
‘ I had the pleafure of receiving on the 
15th of May, the firlt copy of my Hijfoire 
Celefte Frangaife, the refult of twelve years 
labour, which finifhes the account of the 
50,000 fixed ftars,apon which my nephew, 
Michel Lefrancgais, has employed the belt 
part of his youth. I have found alfo fome 
obfervations made by d’Agelet, before he fet 
out on his voyage round the world, and. 
thofe by which Citizen Darquier ter- 
minatec his glorious aftronomical career,at. 
the age of eighty-three. 
The obfervations of Tycho, Flamftead, 
Picard, Lacaille, and Matkelyne, have 
been the foundation on which the whole 
progrefs in tne fcience of afironomy has 
been built; theories the moft profound, 
calculations the moft learned, will not 
furpafs them, either in importance or du- 
ration. The obfervations alone will furvive 
us, and obfervers, whom, fome would fre= 
quently attempt toderide,may confolethem- 
felves; they will be the only aftronomers to 
whom, long after their deceafe, hymns 
‘of praife and gratitude will be offered by 
our fucceffors, and by pofterity. 
Lefrangais Lalande, my nephew, has 
continued his oblervations and calculations 
of 3000 declinations, and rooo right afcen- 
fions, of the principal: ftars, each one 
having been the object of his frequent at- 
tention. TThefelong and difficult labours 
have obtained for hima place in the Natio- 
nal Inftitute. Madame Lefrancais La- 
lande has continued the reduction, to their 
proper places, of the 50,000 fixed ftars, 
an immenfe work, to which fhe has devoted 
herfel£ 
