ASTRONOMY. 



among thnao that arm tho largest and brightest, in which 

 the nebulous matter is dispersed very capriciously, no 

 regularity i* perxvptihle. Among the latter, i 

 ..united at 273 42*01 right ascension, anil UHV 15' of 

 north polar distance (Fig. 85), nay be instanced, bent.,- 

 of tha lm|K of the. large Greek omega, and having no 

 symptoms of rosolvabdity apparent Among the more 

 regular forma, are tho*) termed unnuAir nebul* and 

 coerv nehnlir. Tin- t5m> object situated at AH' 

 right ascension, and 41 ,'n'i of north polar distance 

 (Fig. 86), anJ which U largo cn.<n ;h to lv perceived a* a 



f tint p.! h of li^ht in a small telescope, is among the 

 Burnt instances of the former kind In tins, the tin 

 rounding ring appeared, in tin- two foot mirror of Sir .1 



II. i -.:..!. I-. b .ll\ id. .1 I lit. i t>.., I M.I I., 1 1. - . 1,1 it ill tin- 



gn>at teleeeope . : 1 1 I UMNO, tha whole take* the form 



of a spiral, an<l many ouriout detail* become visible. 

 The smaller nolmla Mow (here represented a* ipiite 

 dt-U.hedi. appears U> IK' conn.-.-tisl with the larger Kxly 

 by a jnojri -tin,.; biai. v line specimen of 



the more simple and rare form of annular n, biihr, in 

 that situated in the constellation . Kg S"), at 



Ml* 4V Of light aSMMMO. itn. I .': 11 of i.oi 111 p. .hi- 

 distance. It U not .|iiito dark in the centre. Tlu> lorm 

 uhf will IK. M. ss, tin- point. si 



i ii, I being attached apparently to a itar, which appoan 

 like a stellar nucleus. (See folio platoa). 



In (be circular, or globular f orm of nolmlir, thedegrwa 

 of 0, tlu- ni-biiloiis ni:itt.T towarils lli.-ir 



iwovlision 



1- I,. . Mi kkpohl .listaiii-- 77 .V.I', th.'tv is tittl.' or no 

 coii.lni.itioii to:ti.U tin- iniil. lli>. In Km. '.XI, 

 asoension Vtf I:: . nortli p..lnr distance In7 1 , t!i. 

 densation is con- ,i. i i 1 !\ m.,i.. inark.'.l. In !'. '.I I . 

 right ann-ii^ioi. .hsl.in,.' 17 <','. tln> 



of MiialliT .'Xti'iit tli. in HI tlio 



hut instance, but U'tt.r .l.-tinr.l an. I nni.-h nioi.' liintions. 

 In I .11 69 39", noiili I-..I.H .ii-.i.iii. .. 



68 -in. tl' .ntt.il |,oitioii Ufomcn nlnuwt st.'lln. 

 |,|^ :.in , like .> well .I. iim.l i<t:ir MM ii'iin.1.,.1 by a halo. 

 The ditl'rivnt dixro-s of .oinlfiisation IV.MI;IIIU|I|I> in 

 the*e obj.vt>. K.l ll.i-.li.-l to niia.iiu' tli.it the n.'luiloiis 

 mat t.i. in tin- i-.'iirse of ages, nn.li iw.-nt .oiiM.l.Titlile 

 chanues, aiul tlmt. having condensed gnMluslly, the 

 Dbulw tiimlly . iui.-.l l..\ U-itiming stars. Theee obaugee 



were o Mow that they had not yet Nvn pcnvinvl ; but 

 it was visible, by annparinj; them together, that itioh 

 pn.Kibly was the case. In some oases, the central star 

 or start was distinctly visible. Such an object is por- 

 ceired at right asoension -'.'.'> .'>', noitli polar dist.-tnoo 

 M -I v ''';: !>:! '>- '" wliich the nebula is evenly ili>lii- 

 but.sl round the st.-ir At riijlit a^.-cnsion '.', 1 l.i . noitli 

 .lisiance HH.r'60' (Fij?. JM\ an elliptic ncbnl.i 

 Msible, with a small star situated in ea.-h of tin- foci of 

 tho ellipse ; and at Fig. SW, right ascension Sd' o , north 

 polar OUtance ft6 &4 . '. of stars is o.iv;rei;alcd 



at tlio centre of a small nebula. In those winch \\oiv 



!y bri.;hl throughout the whole disc, llcrschr! , 

 ], . lui'i-.l that the star was not \i-ible on account of its 

 f.nntness, orfi, .urioun.lc.l by a .Icnse ncbulo 



Such Mil one is situate,! at ii-.ht ascension I till'' I'J', 

 1101 th polar distance o I I 



Among tl. most curious forms of the ncbulir, those 



which aii< double take a pioimneiit. place In t! 



both the components are sometimes of equal magnitude 



a.sccnsi,,n 171 '.M . north polar distance 



66 31 . and similar in every respect, or like those at 



ascension 1 1(1 oS , noilh polar ill . 

 ..'.and l-V; !>;), right ascension l.xi IS. u,,ith 



jx>lar dutaiioe 84 36 , where th.-\ aic of me ulai 

 and coudeiuation. In all these examples IhecomponentM 

 are joined together by the surronndm>; nebulosity; but 

 in some oases the two nebula- are .pule disluul. as in 

 I lixl, unlit as.vn.iion :; f.' IS, nortli polar .!i-.iaiic.> 

 In such cases, llerschel imagined he peivci\e,l 

 h> iiiptoins of tho gradual formation of a .i.ni/./.' star, tlio 

 Uebulous matter of which tlicy aie formed, cond.'i 

 l..ai,U l of alliaction. It will api'ear I'loni 



'.hat the nr/iM/ir, pro[>i>rly so called, according to 

 ir from belli,; such important 

 cU a* the clusters, the latter K'in: i, at . 

 t ions of star*, the nebula- onl\ the material .1 

 or, at most, a double star. Hut it would be ha/ardous 



that any particular nebula was nr, --.ol\ able. 

 gigantic telesco : . i;.-..e has >!,.. u that many 



hitherto deeiiusl of this natu of iniin 



in. -i able stars, Very dlll'erent. from the MII:;!.- individual 



hich llris, i, el thought It was prob.ible K would 



> become. 



The suppositions relative to thin nebulous substance, 

 which llerM-hel tlioii ; ht to bo so plentifully soattcied 

 through spaiii, and the changes wliich he surmised that 

 it underwent ill the course of tune, led the celebrated 

 astronomer l.-iplaeo to form a similar hypothesis on the 

 loi in.iiion of tlie solar system, and the progressive ,i, 

 l|imeiit of the Uxlies of which it is Composed, from one 

 single and primitive mass of nebulous mallei'. lie MI p. 

 I .'-,.1 that the sun was originally inclnd. .1 ..m.-n,; the 

 nebula-, wln.-h ,-\ I. luUnl as far as thu most distant planet, 

 and was endowed with a rotary motion round the c.-nn.-. 

 and that, in thooourse of a;-,es, this gaseous subs! 

 1,. .-.Hue more condensed towarils the cenlic. !, .ivm- the 

 evl. u. , r poitions in the form of immense iin.-.s. still pie- 

 sei-Mii;; their re\oKing motion, precisely similar to tho 

 ring of Saturn as at present existing. l-'iom many 

 dub rent causes it was impossible for those rings to exist. 

 in that form, and they tinally broke up into globular 

 masses forming the diileient p lands |:\ tins means he 

 explains the n-volntion and lotatiou ot the plan, 

 bodies in one direction, as Well as of their satellites. 

 formation of comets, ,tc. K\en the rodiacal li.;ht was 

 fully explained on tins hypothesis. The nebulous matter, 

 as ho conjectured, was not .pule condensed, but still 

 sin i, .milled the sun in a \er\ dillu.ed state, and by the 

 lotatiou of that body on its asis, took a lenticular fonn, 

 as Was observed to be the case with many of the nebula- 

 already discovered. Thus the threat nebula of Audio 

 in.-da is of this elliptic form ; and dillei, of 



elhpticiU will I*. S.-.-H fiom the lii,Mires iii the folio plat* 

 (Figs. 101, In-.', and In:, i. win. h are sou-- ..I those 

 actually obsurvud by Sir .1 llernchel 



