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224 De Lalande’s Hiftary of Aftrenomy for the Year, 1800. { April x, 
The account of the aftrolabe planifphere 
difcovered by Gail in Synefius, has prompted 
Delambre to give a long Memoir on the hiftory” 
of aftrolabes. 
. Burckhardt has difcovered a formula repre- 
fenting the magnetic needle’s declinations, 
ebierved at Paris fince 1530. It appears, its 
declination at Paris is 860 years; tat the 
greateft declination weft is 30°.4' and takes 
place in 1878: the greateft eaftern is only 
re ies 
The printing of tables of fines to thoufandth 
parts of the circle has been completed, De- 
jambre puc the laft hand to them. 
Prony, at the Bureau du Cadaftre, has alfo 
calculated more fully the decimai tables. 
in the Ephemerides atYienna, for 1300 and 
1808, “Trieinecker has made a colleétion of 
all the calculations of eclipfes obferved fince 
1747, from thence to deduce fhe longitudes 
of the European and American cities, and the 
errors in the tables. Never was fo great a 
calculation of eclipfes; this able aftronomer 
has by this rendered government a moi im- 
portant fervice. 
Goudin has by hisAnalyfis fully determined 
the eclipfe of 1847, the moft confiderable of 
the new century. Duvaucel, who has de- 
lineated eclipfes for 30 years pait,has likewife 
delineated this for every country on the globe, 
By his diagram it appears that it will be an- 
nularin England, Franee, Turkey and even 
Cochin China. : 
Duvaucel has alfo delineated the eclipfe of 
February 11tb,1804, which will be total and 
in fome countfies annular, according to the 
fun’s altitude. It is fuppofed fome voyages 
will be undertaken on this occafion for deter- 
mining the differences of the fun’s and moon’s 
diameters, the irradiation and infleGion. 
The diagrams of eclipies have hithertoappear- 
ed-in the Ephemerides of Paris terminating 
with 1800 5; and in thofe of Bologna, which 
extend as far as 1816: there is but one dia- 
gram for 1804; four are wanting, viz. 1802, 
1803, 1806, and 1807. - Duvaucel propoits 
to conitrué them, particularly the two iaft. 
he Memoirs of the French National In- 
fitute, vol. ii. contzin calculations of two 
comets, and feveral eclipfes ; the theory of 
the moon’s fecular equations, by Laplace, is 
alfo to be found in the Mecangue Celefte, that 
important work from which teveral extracts 
were publithed by Briot, in the Magazin En- 
cyclopedique. 
In the Philofophical Tranfactions for 1799 
there isa new method of diicovering the lon- 
gitude by two altituc$s of the fun, and the 
interval of time elapfed, by Mr. Lax, Aftro- 
nomical Profeflor at Cambridge. Alfo a 
fourth catalogue of ftars, by Herfchel, in 
order to afcertain their degree of light. 
The Tranfactions for 18co contain a very 
curious Memoir by Herfchel, on the power 
which telefcopes pofiefs of penetrating into 
fpace ; viz. réndering vifible very remote 
and faint objects, which, by their want of 
~ 
‘light, would be imperceptible were it not fcr 
the affiftance of inftruments ;- ufeful remarles 
on the difference between that force of light 
and that of enlargement ; on the feveral cafes 
towhich either may apply and the meansof pro- 
curing a proper degree of light. Herfchel like- 
wife calculates the lofs of light occafioned by 
mirrors, To him it appears that the greateft am- 
plification does not exceed what is produced by 
a telelcope of from 20 to 25 feet. The 
opinions of fuch a celebrated optician are 
worthy of credit. In the Traniattions for 
1800, Herfchel givesa paper on the different 
influence of folar rays; the yellew rays, he. 
remarks, illuminate moft, while the red com= 
municate the greateft degree of heat. In vol. 
v. of the Edinburgh Tranfactions. Mr. Play- 
fair has given a formula for the figure of the 
earth. 
Among other works which deferve a place 
in the hiftory of aftronomy, is a geometrical 
work by Arbogaft. It contains an applicazion 
of the calculus of derivation, to feries pro- 
ceeding according to the fines or confines of 
the multiples of the fame angle. ‘ 
I have received the Ephemerides of Milan 
for 18co: the perturbations of Mars are 
calculated by Oriani ; “his tables of Mars will 
form a part of the ephemerides for 1801. I 
have likewife received the ephemerides of 
Rome, by Oddi, who occupies the obferva- © 
tory Gaetani, and the Nautical- Almanack 
for 1804, tranfmitted to us by fir Jofeph 
Banks, with hisaccuftomed zeal. 
During the commencement of the revo- 
lution the National-Obfervatory was negle@- 
ed: as foon as I became Diredtor, I folicited 
new inftruments; and Mechainon his return 
from his voyage, feduloufly employed him- 
felf in feeing the neceflary reparations made. 
By the month of Julythenew inftruments 
were erected, but not until the 22d of -Au- 
guft was Mechain enabled to begin his obfer- 
vations of the moon. Bouvard fupplies his 
place wih zeal, and Paris may fhortly boaft 
aferies of obfervations equal to thofe made. 
at the Obfervatory of Greenwich. ~ 
The mural quadrant, of 7Z feet procured 
by Bonaparte, has been ere€ted. Tothe cen- 
tre Lenoir has added an ingenious machine, 
which eafes the central axis of the weight 
of the telefcope, varying as the elevation of - 
the telefcope is changed.. A mural of five 
feet, conitruéted in England, by Siffon, in 
1743, and which I poflefied at Berlin in 1751, 
has been placed on the northern fide. An 
excellent tranfit-inftrument, by Lenoir, has 
been placed in the meridian, and fights have 
been fixed up, north and fouth, at great dif- 
tances, fo that the telefcope be precifely in 
the mieridian. It is to be hoped that a co- 
lumn will be raifedin the plain, with alight 
kindled in the evening, to ferve during the 
night. 
€. Caroche has finifhed a telefcope of 22 
feet, and fixed it without the fmall mirror, 
in the manner of Lemaire and Herfchel, ee 
S 
