VOL. LXXV.] PHILOSOPHICAL TRANSACTIONS. OfcSO 



become resolvable nebulae from the same cause. The distinctness of the instru- 

 ment is here also concerned; and as telescopes with large apertures are not easily 

 brought to a good figure, nebulous appearances of both sorts may probably come 

 on much before the distance annexed to them in the table. 



Section of our sidereal system. — By taking out of this table the visual rays 

 which answer to the gages, and applying lines proportional to them around a 

 point, according to their respective right ascensions and north polar distances, we 

 may delineate a solid by means of the ends of these lines, which will give us so 

 many points in its surface ; I shall however content myself at present with a sec- 

 tion only. I have taken one which passes through the poles of our system, and 

 is at rectangles to the conjunction of the branches which I have called its length. 

 The name of poles seemed not improperly applied to those points which are QO 

 degrees distant from a circle passing along the milky way, and the north pole is 

 here assumed to be situated in r. a. 18t>° and p. d. 58°. The section represented 

 in fig. 9, is one which makes an angle of 35 degrees with our equator, crossing- 

 it in 1244. and 3044- degrees. A celestial globe, adjusted to the latitude of 55° 

 north, and having <r Ceti near the meridian, will have the plane of this section 

 pointed out by the horizon, and the gages which have been used in this delinea- 

 tion are those which in table 1 are marked by asterisks. When the visual rays 

 answering to them are taken out of the 2d table, they must be projected on the 

 plane of the horizon of the latitude which has been pointed out ; and this may 

 be done accurately enough for the present purpose by a globe adjusted as above 

 directed ; for as gages, exactly in the plane of the section, were often wanting, I 

 have used many at some small distance above and below the same, for the sake 

 of obtaining more delineating points ; and in the figure the stars at the borders 

 which are larger than the rest are those pointed out by the gages. The inter- 

 mediate parts are filled up by smaller stars arranged in straight lines between the 

 gaged ones. The delineating points, though pretty numerous, are not so close 

 as might be wished ; it is however to be hoped that in some future time this branch 

 of astronomy will become more cultivated, so that we may have gages for every 

 quarter of a degree of the heavens at least, and these often repeated in the most 

 favourable circumstances. And whenever that shall be the case, the delineations 

 may then be repeated with all the accuracy that long experience may enable us to 

 introduce ; for, this subject being so new, I consider what is here given partly as 

 only an example to illustrate the spirit of the method. From this figure how- 

 ever, which I hope is not a very inaccurate one, we may see that our nebula, as 

 observed before, is of the 3d form : that is, a very extensive, branching, com- 

 pound congeries of many millions of stars ; which most probably owes its origin 

 to many remarkably large as well as pretty closely scattered small stars, that may 

 vol. xv. 4 T 



