152 
theory of aftronomy: he was not merely a 
calculating, but likewife a practical aftro- 
nomer. Whilft yet refiding at Verfailles, 
he purchaled at his own expence fome in- 
ftruments; and the Duke of Ayen,* a 
great |. ver and patron of aftronomy, who 
efteemed Méchain on account of bis talents 
and amiable qualities, lent him his. La- 
Jande wifhed to procure him an opportu- 
nity of making himfelf known to the Royal 
Acedemy of Sciences. Méchain obferved 
at Verfailles, on the 14th of April, 1774, 
the cccultation of the Bull’s-eye by the 
Meon:, he wrote a {mail differtation there- 
on, which Lalande laid before the Acade- 
my. It was declared worthy of the ho- 
Hour of being received into and printed in 
the colleétion of Memmoires prefentées al A- 
cademie.+ By this and other oblervaticns, 
and by the calculation of fome difficult or- 
bits of comets, our Méchain became more 
and more advantageoufly known to the 
Academy and its members. 
In the year 1781, he had the good for- 
tune to difcover two comets, on the 28th 
of June and the oth of O&ober: he pur- 
fued their courfe, and at the fame time 
calculated their paths. Of the French alf- 
tronomer:, he was one of the firft who mcft 
carefully obferved the new planet difcover- 
ed in that year by Dr. Herfchel, and cal- 
culated its path in feveral parabolas and in 
acircle. The firft el’iptical path which 
Laplace calculated, and by which this new- 
ly difcovered heavenly body, -which had 
befcre that been taken for a comet, was 
raif-d to the rank of a planet, is founded 
on four very accurate obfervations by Mé- 
chain. 
In the following year, 1782, the Acade- 
my of Sciences adjudged to him a prize for 
a differtation relative to the celebrated co- 
met which appeared inthe years 1532 and 
1661, and which was by fome aftronomers 
expected to return inthe year 1789. Mé- 
chain proved in this excellent- prize difler- 
tationf, that the comet of 1532 and of 
766 was not one and the fame, but two 
guite different heavenly bodies, and that 
they would not return in 17893 which af= 
fert.ion was likewife completely juftified by 
the event. This fo honorably acquired 

* Of the family of the Noailles, grandee 
of Spain of the firft clafs, knight of the gol- 
den fleece, captain of the Gardes-du-Corps of 
the king, and honorary membervof the Aca- 
demy of Sciences. 
T <difi. de P Acad roy. des Sc. de Paris pour 
Ll Annee 1774, p. 84, and Mémoires, p. 21. 
{ Mémoires de Mathem. et Phyf. prefentées a 
l'Acad. R. des fo par divers Savans, et lus dans 
fes Affimbless. Tom x. Paris, 1785, pf: 333s 
Memoirs of Mechain. 
[Sept. i, 
prize opened to him the gates of the Aca. 
demy; and he was in the fame year ad- 
mitted as Affocie ordinaire into this fociety 
of the moft celebrated and learned men of 
France. 
How diligent and indefatigable an ob- 
ferver of the heavens Méchain always was 
and {till is, appears from his having, fince 
the year 1781, diflcovered eleven new co- 
mets, two of them laft year, the one in 
Auguft, and the other about Chriftmas, 
during the fevere winter of 1799. And 
although Meffier may furpafs him as to the 
number of fuch difcoveries in the heavens ; 
yet it may be affertcd of Méchain, that no 
alironomer yet, either of the prefent or any 
former age, has fingly difcovered,, ob- 
ferved and calculated fo many comets. 
Not Jefs than twenty four new paths of 
comets has he calculated according to dif- 
ferent methocs ; and it may be faid of him 
with truth, that in him is united at the 
fame time the merit of a Meffier and of 
a Pingré. 
In the year 1780 the Duke of Ayen 
had formed the defign of having a large 
military map of Germany, and a fimilar 
one of the theatre of war in Italy, drawn 
up. This plan the Office for Foreign 
Affairs had before wifhed to put in ex- 
ecution, but from a want of money it was 
deferred from time to time. The Duke, 
therefore, refolved to have thefe maps pre- 
pared at his own expence, and engraved, 
under the condition that the War-office, 
and the Office for Forcign Affairs, fhould 
buy a certain number of copies, and com- 
municate to him all their maps, manu- 
fcript draughts, plans-de-compagne, and 
other materials in their pofleflion, which 
might be ufeful for the new maps. Thefe 
conditions were agreed too: the Duke had 
befides, of his own, a rich colleétion of 
the beft and moft fplendid maps ; and col- 
lefted, for the purpofe, a great number of 
vaiuable draughts and memoirs by means 
of his friends and relations, many of 
whom were generals and marfhals of 
France, and had themfelves made cam- 
paigns in the above-mentioned countries. 
All thefe excellent materials he caufed to 
be reduced to one {fcale by his aide-de- 
camp and geographico-military engineer, 
affilied by ‘everal draughtimen. But this 
was not fufficient for the formation of ac- 
curate maps. It was requifite to have an 
altronomico-geographical net, and care- 
fully determined points, by which the de- 
figners mult be direéted in the incorpo- 
rating of particular maps. Jhis moft. 
important partof the bufineis the Marquis 
committed to Méchain, as it had before 
been 
“ 
