of the Sun and Solar Syftcm. 279 
own proper motions. However, I forbear entering too much 
into refined confederation ; what we are chiefly to determine at 
prefent is, an outline or fketch of what many repeated, and 
farther extended, obfervations muft ripen lo far as in time to 
enable us to apply more particular calculations. 
The motions of « Lyras and s Urfae majoris towards the 
north are placed in the firft table ; it will, therefore, be pro- 
per to fhew the general law by which the apparent declinations 
of the flats, at prefent under confideration, are governed. Let 
an arch of 90 degrees be applied to a fphere reprefenting the 
fixed ftars, fo as always to pals through the apex of the folar 
motion : then, while one end of it is drawn along the equator, 
the other will defcribe, on the fpherical furface, a curve which 
will pafs through the pole of the equator, and return into it felt 
at the apex. This curve, to borrow a term from natural his- 
tory, is a non-defcript as far as I can find at prefent, and may 
be called a fpherical conchoid from the manner of its genera- 
tion. The law then is, that all the ftars in the northern he- 
mifphere, fituated within the nodated part of the conchoid, 
will feem to go to the north by the motion of the folar fyftem 
towards its apex ; the reft will appear to go fouthwards. A 
fimilar curve is to be delineated in the fouthern hemifphere, in 
the nodated part of which the fame appearances will take 
place. It will require but little attention to fee the truth of 
this conftrudtion. 
Suppofe the great circle A cam, fig. 5. of which the gene- 
rating quadrant mn is a part, compleated ; then will it in ter feet 
the equator EQT in two oppofite points me. Now, lince the 
apex A, by the hypothefis, is fo mew here north of the equator, 
the great circle will always make fome angle AwQ^with it ; 
and the point n, which is 90 degrees from the inteife&ion m 
Vol. LXXIII 
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