Mr. Herschel's Catalogue of Double Stars, 41 



14. begins here at 25, and the fame is done with the other 

 clafles. 



Mofl of the double flars in my fird.colleclion are among the 

 number of thofe ftars which have tlieir places determined in 

 Mr. Flamsteed^s exteniive catalogue ; but of this colledtion ^ 

 many are not contained in that author's work, I have therefore 

 adopted a method of pointing them out, which it will be proper 

 to defcribe. 



The finder of my reflector is limited, by a proper diaphragm, 

 to a natural field of two degrees of a great circle in diameter. 

 The interfeclion of the crofs wires, in the center of it, points 

 out one degree ; and by the eye this degree, or the diitance 

 from the center to the circumference, may be divided into |, 

 I, I, 4, and f. Thus we are furnifhed with a meafure which, 

 though coarfe, is however fufficiently accurate for the purpofe 

 here intended ; and which, if more than two degrees arc 

 wanted, may be repeated at plealure. 



In fuch mcafures as thefe 1 have given the difbance of a dou- 

 ble flar, whofe place I wanted to point out, from the nearefl 

 ftar in Flamsteed's Catalogue. And fince, befides the 

 diftance, it is alfo required to have its poiition with regard to 

 the flarthus referred to, I have ufed the neighbouring liars for 

 the purpofe of pointing it out. 



The ufefulnefs of this method is fo extenfive, that I fliall be 

 a little more particular in defcribing its application. When a 

 ilar is thus pointed out, as forinftance the32d in the firfl clafs, 

 where it is faid, '* About Ci degree f. preceding the 44th Lyncis, 

 *^ in a line parallel to ^Urfae majoris ao^ the 39th Lyncis ;" we 

 are to apply one eye to the finder, and placing the 44th Lyncis 

 into the center of the field, we are to look at 5 Urfae majoris 

 and the 39th Lyncis in the heavens with the other eye by the 

 Vol. LXXV. G fide 



