AST 



the diflance of Saturn from the fun, has donhkd the boundj 

 fonnerly afligiicd to the folar fyflem. Vv'c are aifo in- 

 debted to him for a vanety of obfcrvations 0:1 feveral other 

 intereltinfr afhonomical f!.ih;t.£is ; fiich as tiie difcovejy of 

 two additional fateilites to Saturn, of wliich the iminbc-r is 

 now icven ; a new method of meafiiring tlie lunar moun- 

 tains ; the rotation of the planets on their ax(.s ; on the pa- 

 rallax of the ii:;ed liars ; cata!;)trnes of double, triple ftars, 

 &c. J of nebuls ; and of the proper motion of the fun and 

 fo'ar fylliem ; the accounts of which, together with many 

 other valui'hie papers, he has coniir.unic^sted from time to 

 time in difFcr.;nt parts of the Philofophical Tranfaclioas. 

 Wiihin this lad year alfo another new planet has been difeo- 

 vered by M. Fiazzi of Palermo, between Mars and Jupiter, 

 to which he has given the name of Ceres Ferdiiiancia ; and 

 even the difcovery of a third has been announced in fome of 

 the foreign journals ; \>ut for any regular aecourt of this we 

 mull v/ait for further information. See Georgium Sidus, 

 Ceres F'erdrnandia,?iv.d Pallas. 



It is with great plcafure we obfcrve that at no former 

 period has this fcience been cultivated with more ardour 

 than it is at prefent, both in this and evvtiy other country 

 in Europe. In France, the phyiico-matheir.atical part of 

 the fcience has been greatly improved and extended by the 

 celebrated M. la Place, who, in his elaborate work, the 

 " Mcchanique Celefle," has inveftigated all the phasnomcna, 

 whicii the attraftion or univerfal gravitation of matter can 

 produce on the forms and motions of the celsftial bodies, 

 by their mutual aftions on each other. M. Lalande, the 

 patriarch of ailronomers, is alfo ilill indefatigable in his pur- 

 fuits, and by the zeal he conilantly m.anifeils for the interefts 

 of this fcience, has greatly promoted thelludy of it in almoll 

 every quarter of the globe; but particularly in Germany, where 

 M. von. Zach is equally affiduous in forwarding its im.prove- 

 ment. In all its collateral branches alfo we obferve a degree 

 of afti\^ty that has never been exceeded. New admeafure- 

 ments of the earth have been undertaken both in this coun- 

 try and in France, which, from the great improvements of 

 inftruments, -•'id the (kill and indullry of the obfervers, 

 promife a greater accuracy in the refults than could have 

 been obtained bv thofe who were form-erly engaged in this 

 undertaking. From the zeal and abilities of major Mudge, 

 in particular, who is now employed by our government to 

 make a trigonometrical furvey of the country, we may ex- 

 pect the molt accurate details on this fubjeft that have ever 

 jet been prefcnted to the public. 



We (haU conclude by obferving that there flill remains a 

 -number of difcoveries to be made in this fcience. We have 

 not yet determined the times of rotation and the proper 

 figures of fome of the planets and their fatellites ; nor do 

 we know with fufScient precilion the maffes of thofe bodies. 

 The thtor)' of their motions alfo confifts in a fcrics of ap- 

 proximations, of which the convergence depends both upon 

 the perfection of inllruments, and the progrcfs of analyiis, 

 and which for that reafon ought to acquire continually new 

 degrees of exadtnefs. Oblervations On the return of comets 

 already obferved, as well as on"thofe which may hereafter 

 appear, fhould liktwii'c be made with great care, and par- 

 ticularly on fuch as may entirely change their orbits, as it 

 has been conjectured was the cafe", by the aftion of Jupiter 

 on the one which appeared in 1770 ; as alfo fuch accidents 

 which the proximity, and even the fliock of thefe bodies, 

 may occafion to the planets and their fatellites ; fuch are 

 'the principal objefts which fhould engage the attention of 

 future allronomers. 



For more particular accounts of the writings and authors 

 ©n this fcience, the reader may confult Wcidkr's " Hiilory 



Vol. in. 



AST 



of Aftronomy," which is brought down to the year 1737, 

 as alfo " Bailly's Hiilory of Ancient and Modern Allr o- 

 nomy," ^'^ontucla's " Kiftoire des Mathematiqucs," and 

 the firll volume of Lalande's Aftronomy. The more mo- 

 dern and popular works on the fubjeft are numerous and 

 well known ; as thofe of Emerfon, Eergufon, Long, Bon- 

 nycaftle, &c. ; in the latter of wliich, in particular, thi 

 elementary parts, and general outline of the fcience, are 

 d'.feribed with great perfpicuity a:id elegance. 



AsTROKOMY is fometimes divided with refpecl to it« 

 different dates, into new and o/if. 



Astronomy, ylncient, is fuch as tlie art flood under 

 Ptolemy and his .followers, with all the apparatus of folid 

 orbs, epicycles, exccntrics, deferents, trepidations, &c. 



AsTROxoMY, New, is fuch as the art has been fmce Co- 

 pernicus, by whom thofe fictitious machines were thrown 

 out, and the conllitution of the heavens reduced to more 

 liniple, natuml, and ceitain pricciplts. 



In Ricciolus's Almagellum Novum, publifhed in 1651, 

 we have the feveral hypothefes of all the allronomers, an- 

 cient as well as modern. — And in Dr. Gregor)''s Elemerta 

 Attronomios Phyfica: & Geometricx, in 1702, the whole 

 modfern aftronomy, as founded on the difcoveries. of Coper- 

 nicus, Kepler, and fir Ifaac Newton. — The fubltance of 

 the old allronomy is given by Tacquet ; and of the new 

 allronomy by Whifton, in his Pnelectiones Ailronomici, in 

 1707. Mercator's Inftitutiones Aftronom.icx, publidied in 

 1676, contains the whole dodtrine, both according to the 

 ancients and moderns ; and Dr. Keill's Introdufiio ad vc- 

 ram Aftronomiam, ia 1718, comprehends the modem; to 

 which might be added Vince's Aftronomy, in 2 vols. 4to. 

 1800; and his Praftical Aftronomy, 4to. 



ASTROPECTEN, in Natural Hijlory, a name given 

 by fome authors to a fpecies of ftar-filh, compofed of a 

 body, or central nucleus, furrowed in the manner of the 

 fliells of the common fcallop, and parting into five princi- 

 pal rays, from each of which there iflue feveral traufverfe 

 procedes, covered with a hairy down. 



ASTROPODIA. See A'steria, and SxAR/on^. 



ASTROSCOPE, in Aponomy, a kind of aftronomical 

 inftrument, compofcd of two cones, on whofe furface the 

 conftellations, with their ftars, are delineated, by mean* 

 of which the ftars may eafily be known. 



The aftrofcope is the invention of Wil. Schukhard, for- 

 merly proftlfor of mathematics at Tubingen, who pub- 

 liflud a treatife exprefslv on it, in 1698. 



ASTROSCOPIA, 'from arrj,7?<ir, and <rr.',T'i-, I confi- 

 der, the art of obferving and examining the ftars by means 

 of telefcopes, in order to difcover their nature and pro- 

 perties. 



Huygens improved this art confiderably in his " Aftro- 

 fcopia Compendiaria Tubi Optici molimine liberata," where 

 he ftiews how to manage tlie largeft glalfes without help 

 of a tube. See Telescope. 



ASTROTHEMATA, in Apoh;y, the places or po- 

 fitions of the ftars in a theme of the heavens. Vital. Ltx. 

 Math. 



ASTROTHESIA, from ar-r.^, and T.fn^i, I phut, is 

 ufed bv fome for a conftellation or image in the heavens, 

 compofed of feveral ftars. 



ASTRUC, John, M. D. in B'logrobhy, a learned phy- 

 fician, and author of numerous medical and philoiophical 

 works, was borne at Sauve, a confiderable town in Lower 

 Languedoc, on the 19th of March lfiS4. He was early- 

 initiated into the knowledge of the clafiics by his father, 

 and was fent to complete his education to the univerfity at 

 Montpelier, where ia 1 700 he commeaced maftci of aits, 

 Z acJ 



