$809.] 
Englefield, Prosperin, Olbers, Burck- 
hardt, and Bouvard. ; 
M. "Busekthar dt has made us moré ac- 
curately acquainted with the orbits of 
many ancient comets, the observations of 
which he found unpublished in the depots 
of the Observatory ; no one of these new 
comets resembles those which were al- 
reatly known. It may appear astonish- 
ing, that of ninety-seven comets, which 
have been calculated, one only should 
have yet returned. Are their orbits pa- 
rabolic or hyperbolic? Or may they not 
in their courses have experienced attrac- 
tions similar to that which has caused 
the comet of 1770 to disappear? 
“Men of leariting have been equally in- 
tricsted by other “observations of a dil- 
ferent. kind. _ M. Herschel continued his 
description of the heavens; his cata- 
logues of double, triple, and quadruple, 
stars, of nebule with or without. stars, 
with round discs like that of the pla- 
nets, or discs of an irregular form. He 
endeavoured to determine the various 
motions of these bodies, which he makes 
to revolve round their common centre of 
gravity. Ele has found in Saturn's ring, 
by the observation of aremarkable point, 
the motuon of which he has measured, a 
rotation of ten hours and a half, at the 
same time that M. Laplace demon- 
strated, by his analysis, that this ring 
could not be supported without a rota- 
tion of about ten hours. 
M. Schroter applied himself particu- 
larly to giving circumstantial descriptions 
of the various planets, to measuring and 
determining the times of their rotations, 
He di-covered that of Venus by the ob- 
servation of a mountain, situated at the 
souther, point of the crescent... This 
rotation is performed in 23 hours, 21 mi- 
nutes: he ‘found, by analogous means, 
that Mercury- and Mars revolve in 24 
hours and some minutes.- 
By this rapid statement it appears, that 
since 1789 astronomy has been im- 
proved in all its branches ; 
sensible inequalities of the planets have 
been explained, and determined; that 
the Tables have acquired both a greater 
and more durable precision ; that the 
wsual calculations are rendered more ac- 
curate; in short, that observations have 
Inade us acquainted with bodies totally 
new to us, and have magnified to our 
Progress of the Sciences. 
that all the. 
eves, and to our understanding, the ad- 
mnirab! e whole which forms the system of 
the world. All these advances, with 
thew particalar-details, may be found io 
297 
the large Treatises on Arendaee, pubs 
lished by M. Lalande, in 1792, and by 
M, Schubert, in 1798. ; i 
MAT EMATICAL PITysics. - 
The revolution effected in chemistry, 
within our time, must, in some measure, 
have diverted from their: habitual pur- 
suits. our natural philosophers, who per- 
ceived in a science, so nearly related to 
their own, a career opened before them, 
promising more numerous discover:es, 
We shall, however, have to relate, in phy- 
sics, some curious labors and inferesting 
inventions. 
The balance of Torsion, with which 
Coulomb so successfully demeraned the 
law of electrical attractions and repui- 
sions, was sufficient for him to prove, 
that the magnetic phenomena are subject 
tua similar law; to measure the smai- 
lest effects of macnetism; to find a high 
degree of temperature, which causes 
them tetally to disappear; to shew that 
magnetism is not, as it was supposed, a 
property peculiar to certain bodies, but 
that it exists in all, even in those whick 
appear the -most ‘destitate of it. By 
means of the same balance, he measured 
the resistance whieh fluids oppose ta 
motion, the law of wite is expressed by 
“two terms, of which Néwton had found 
-only the fist because the second be. 
comes sensible only in very slow mo- 
tions. 
Coulomb devoted is whole life to the: 
improvement of dipping and declining: 
compasses. The dip was particularly dif 
ficuit to obtain; because MIM. Coulomb’, 
Laplace, and Borda, had not yet given 
the canons calculated to determine it by 
the number of oscillations; and because 
the compasses were inaccurate, MM. Gil.: 
pin*has just poblished, in the Philcsophis: 
cal Transactions, a long series of obser 
vations, shewing that the inclination or 
dip is subject to diurnal and secular va- 
riations, and that the annual diminution 
is new five minutes, M. Cassini abs 
served the diurnal inequalities of the 
declination with compasses of his own 
invention. M. Biot attempted to de- 
termine, by the observations of La Pey- 
rouse aml M. Humboldt, the position of 
the magnetic equator and its intersection 
with rhe terrestrial equator. M. Hum- 
boldt, in his turn, verifed M. Bior’s 
theory, by new uNeéivations made cons’ 
jointly with M. Gay Lussac. They found, 
that neither the great chains of mouns 
tains, * nor volcanoes, even when bur: 
ing, had any sensible influence on ite 
magnetic 
