BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 609 



Herschel, W.: Synopsis ov the WpvITings of— Continued. 



A. D. Vol. r. 



We shall be able to say that a distant celestial object is so far from 

 \\s, provided the stars of %Yhich it is composed are of a size and 

 histre equal to the size and lustre of such stars as SirUis, Arcinrua, 

 etc. 

 1817 107 'Ml The stars of the tenth, eleventh, and twelfth order of distances are 

 not only more compressed than those in the neighborhood of tho 

 sun, but, moreover, their compression in different parts of the 

 heavens must be very unequal. 

 IX. Of the construction and extent of the milky irai). 

 322 General description of it. 



The sun is within its i)lane, for to an observer in latitude 00°, when 

 at 100° R. A. the milky way is in tho east, it will at the same time 

 be in the west at 280° ; while in its meridional situation it will pass 

 through Cassiopeia in the Zenith and through tho constellation of 

 the Cross in the Nadir. 

 323-4 Examination of the cluster in the Sword Handle of Perseus, with 

 various space-penetrating powers. 



325 [Beside the 863 gauges published in Fhil Trans., 1785, p. 221, above 



400 more have been taken in various parts of the heavens and are 

 not published.] 



326 The twenty-foot telescope cannot fathom the profundity of the milky 



326 If the stars of the 5th, 6th, and 7th magnitudes cannot be supposed 



to be gradually of a smaller physical size ami brightness than those 

 of the 1st, 2d, and 3d, how much less can a supposition be admitted 

 that would require that the stars which, by a long series of ganging 

 powers have been proved to make their gradual telescopic appear- 

 ance should also be gradually of a different construction with re- 

 gard to physical size and brightness from those which we see with 



the naked eye? ., ,, i +u^ 



327 The telescopic breadth of the milky way considerably exceeds the 



extent which, in our maps, is assigned to it. 

 328-30 Observations— sweeps— which confirm this. 



330 X. Concluding RemarJcs. 



What has been said of the extent and condition of the milky way in 

 mv papers on the construction of the heavens, with the addition of 

 this attempt to give a more correct idea of its profundity in space 

 will contain nearly all the general knowledge wo can ever have of 

 this magnificent collection of stars. 



331 Our sun with all the stars we can see with the eye are deeply im- 



mersed in the milky way, and form a component part of it. 



' Wiixi.vji Herschel. 



[ Dated] Slough, near Windsor, May 10, 1817. 



,R1H 108 4-9 Astronomical ohservations and experiments, seleei^d for the purpose of as. 



1818 108 4-9 ^« ^^^^ ^.^,^^.^.^ ^.^,^„,,, ,j. ,j,„ters of stars, and of unrst,oat^ng 



Zw far the power of our telescopes may he expected to reach rnto space 

 ^Zldirectei to amhiguous celestial ohfeets. By «- ^io^am Hkh- 

 SCHEL, Knt. Guelp., LL. D., F. R. S. Read June 11, 1818 

 429 The method of equalization of star light will show the re lative d s- 

 tances of stars; from this a method was explained in Phi T>a„s., 

 18^7 by which means the profundity in space of every object con- 

 sfstilig of stars can be ascertained as far as the light of the telescope 



S. Mis. 31 39 



