1801.] De Lalande’s Hiftory of Afronomy for the Year, 1800 
eomet was only perceivable’for a few days, 
and to the naked eye appeared as a ftar of the 
fifth or fixth magnitude. ‘This makes the 
gift whole orbits have been calculated. Its 
calculation. was alfo made in Germany by 
M. Olbers and M. De Wahl. 
The arduous labour with regard to the 
ftars, which commenced Auguft 5, 1789, has 
been vigoroully continued and happily termi- 
nated by Le Frangais Lalande. He has de- 
termined the places of 50,000 ftars, from the 
pole to two or three degrees below the tropic 
of Capricorn; and with Burckhardt has, com- 
menced a review of the zodiacal conftella- 
tions, in the hope of difcovering fome new - 
planets. Madame Le Frangais having re- 
duced 10,000 ftars, has commenced the re- 
du€tion of the whole number with unexam- 
pled fpirit. 
The clofe of the century has alfo been par- 
ticularly diftinguifhed by the theory of the 
moon. 
June the 13th Laplace made known a new 
refult of the theory, which is a nutation of 
the lunar orbit, the refult of the earth’s 
oblate form. By this inequality we may 
infer, that the lunar orbit, inftead of moving 
with a conftant inclination to the ecliptic, 
moves in a plane, and paffes the equinoxes be- 
tween the equator and ecliptic, inclining to 
the latter at an angle of fix orfeven feconds. 
He finds alfo an inequality of the moon, de- 
pending on the longitude of the node, which 
is fix feconds. 
The courfe of the moon for 1002 years 
was attended with a difficulty now removed. 
The obfervations of the Arabians in the roth 
‘century were of the greateft importance in 
this refpect. 
The Inftitute propofed, as the fubject of a 
prize, the comparifon of numerous obferva- 
tions of the moon, witli the tables to fix the 
epochs of the lunar longitude, of the apo- 
geum and the node. Burgand Bouvard, who 
fhared the prize, have given new determina- 
tions of the moon’s motion, fo well founded, 
that there is reafon to believe their tables will 
never vary more than fifteen or twenty fe- 
conds ; viz. one half or a third lefs than Ma- 
fon’s, publifhed in England. Dr. Mafkelyne 
made him undertake them by determining 
the co-efficients of twenty-four equations of 
Mayer’s tables by comparifon with Bradley’s. 
The equations difcovered by De La Place, 
have brought them to greater perfection, and 
nothing now remains but the latitude. 
Burg has made a calculation of 3233 of 
Mafkelyne’s obfervations, to certify the 
epochof the moon. Healfo determined with 
more correctnefs Mafon’s twenty-four equa- 
tions of the moon. Madame Lavit calcu- 
lated upwards of 500 places of the moon for 
Bouvard’s refearches. 
That able aftronomer Burckhardt, calcu- 
lated lunar tables, according to Burg’s refults, 
Jor the ule of aftronomers fetting out ona 
| 223 
diftant expedition; as there may be fituations 
when it will be important for them to have 
exact calculations of the longitude. 
The French Board of Longitude has ofered 
a prize of 250l. for more perfect lunar tables, 
which will fhortly be obtained. This branch, 
fo important to aftronomy and navigation, 
which has occupied full toa years, is thus 
terminated in the moft fatisfaétory manner. 
De Parceval has concluded the grand ana- 
lytical theory of the moon, giving precife for- 
mule for more equations than are mention- 
ed in the before quoted tables. De La Place 
is likewife occupied on the theory of the 
moon, He has finifhed a memoir of the fa- 
tellites of Saturn and Herfchel’s planet. 
He proves that the fatellite of Saturn has 
an inclination, and afcertains the motion of 
its nodes. 
Vidal has fent the rareft obfervations on 
Mercury, made at Mirepoix. ~ This aftonifh- 
ing obferver, who has done more in this re- 
fpe& than all the aftronomers in the known 
world, has forwarded upwards of 500 obfer- 
vations on Mercury. He has been appointed 
Direétor of the National Obfervatory at Tou- 
Vaute. (15 
Michel Le Frangais Lalande, my nephew, 
finding Mars to be the only planet whofe tables 
were ftill erroncus, calculated anew the ob- 
fervations on that planet. Le Frangais has 
prefented the Inftitute with new tables of 
Mars in tenths of a fecond, from which it is 
apprehended afew feconds error only will be 
found. 
Triefnecker has began a fimilar work 
at Vienna, and Orianiat Milan. Wurm alfo 
made a calculation of the perturbations of 
Mars, by Klugel’s method, to be found in 
the Memoirs of the Gottingen Society, 
Thetranfit of Mercury over the fun enabled 
me to verify the place of the aphelion, and 
by my refult there appears no neceffity for 
changing the tables of Mercury. 
As to Jupiter, we find the correétion to be 
made in the tables +34" inthe oppofition and 
-+30'' inthe quadrature. 
For Saturn the oppofition corretion is 
10”, nearly the fame as the preceding year. 
For Herfchel’s planet I found 9"3 and 
Von Zach had the fame refult after his obfer- 
vations. 
As to the folar tables, I find 8/ors10" too 
much in our longitudes : whether this arifes 
from a retardation in the earth’s motion for 
20 years paft, or from fome error as to the 
mean motion in the conftruction of Delambre’s 
and Von Zach’s tables. However this 
may be, in cafes where precifion is re- 
quifite, Idedu& 10! from the fun’s place. 
Bernier has deduced his obfervations on the 
ftars up to the year 1800 they will foon be 
printed. 
Delambre is obferving with a circle the 
declinations of the ftars of the 1ft 2d and 3d 
magnitude, 
The 
