MAGNITUDE 01* titiktt C£lES*IAl BODIES 287 



The author then proceeded to make direct observations on 

 the fpurious diameters of celeftial bodiesi from which he de- 

 duces the following refults :* 



( 1 .) As the diameters of fixed Mars are undoubtedly fpurious, Spurious diamc- 

 it follows that, with the ftars, the fpurious diameters are larger ^"^ JjJJ 

 than the real ones, which are too fmall to be feen. real. 



(2.) From many estimations of the fpurious diameters of the Sizes are the 

 ftars f it follows, not only that they are of different fizes, but cumftances . ci 

 alfo that under the fame circumftances, their dimensions are 

 of a permanent nature. 



(3.) By this and many other obfervations it appears, that and colours* 

 the fpurious diameters of the ftars are differently coloured, 

 and that thefe colours aTe permanent when circumftances are 

 the fame. 



(4.) By many obfervations, a number of inftances of which They are Iefs 

 may be feen in Dr. Herfchel's catalogues of double ftars, their Wlth h,gU 



£■ • J- i rr » . . ~ , -r • POWerS j 



tpunous diameters are leflened by mcreafing the magnifying 

 power, and increafe when the power is lowered. 



(5.) It is alfo proved by the fame obfervations, that the but not propor- 

 increafe and decreafe of the fpurious diameters, is not inverfely Umi]l V* 

 &s the increafe and decreafe of the magnifying power, bat in 

 a much Iefs ratio. 



(6.) The magnifying power a6ts unequally on fpurious di« Small ftars are 

 ameters of different magnitudes; Iefs on the large diameters, moft Wllarfie<i * 

 and more on the fmall ones. 



(7.) When the aperture of the telefcope is leflened, it will Lefsaperture 

 occafion an increafe of the fpurious diameters, and when in- ^ auf f. s greater 

 created will reduce them. and /"mail ftate 



(8.) U alfo (hows that the increafe and decreafe of the * re ^ * ffeacd 

 unequal fpurious diameters, by an alteration of the aperture 

 of the telefcope, is not proportional to the diameters of the 

 ftars : 



(9.) But that this alteration a£ts more upon fmall fpurious 

 diameters, and Iefs upon large ones. 



(10.) From this we find that ftars, when they are ex- Very fimll tors 

 tremely fmall, lofe therr fpurious diameters, and become ne- a PP earncbulou -' 

 bulous. 



* On this fubjea fee our Journal, Vol. VI. p. 15, and Fig. 1, 

 JPlate IV. 



f See Catalogue of double Stars. Phil. Tranf. for 17S2, p. 115; 

 and foe 1785, p. 40. 



'%> {11.} Many 



