22 9 
and Velocity of the Solar Motion. 
out its situation. It is therefore evident that projectile mo- 
tions must be combined with attraction, and that the motions 
of the stars when regulated in this manner, are not unlike the 
disposition by which the bodies of the solar system are go- 
verned. If we pursue this arrangement, it will be proper to 
consider the condition, and probable existence of such a centre 
of attraction. 
There are two ways in which a centre of attraction, so 
powerful as the present occasion would require, may be con- 
structed ; the most simple of them would be a single body of 
great magnitude ; this may exist, though we should not be 
able to perceive it by any superiority of lustre ; for notwith- 
standing it might have the usual starry brightness, the de- 
crease of its light arising from its great distance would hardly 
be compensated by the size of its diameter; but to have 
recourse to an invisible centre, or at least to one that cannot 
be distinguished from a star, would be intirely hypothetical, 
and, as such, cannot be admitted in a discussion, the avowed 
object of which is to prove its existence. 
The second way of the construction of a very powerful 
centre, may be joint attraction of a great number of stars 
united into one condensed group. 
The actual existence of such groups of stars has already 
been proved by observations made with my large instru- 
ments; many of those objects, which were looked upon as 
nebulous patches, having been completely resolved into stars 
by my 40 and 20-feet telescopes. For instance, the nebula 
discovered by Dr. Halley in the year 1714, in which the 
discoverer, and other observers after him, have seen no star, 
