Dr. Herschel’s Catalogue y &c. 213 
'Arrive at a knowledge of their conftrudtion. In the profecution 
of fo extenfive an undertaking, it may well be fuppofed that 
many things rauft have been fuggefted, by the great variety in 
the order, the fize, and the compreflion of the ftars, as they 
prefented themfelves to my -view, which it will not he improper 
to communicate. 
To begin our xnveftigation according to fome order, let us 
depart from the obje&s immediately around us to the molt 
remote that our telefcopes, of the greateft power to penetrate 
into [pace , can reach. We (hall touch but (lightly on things 
that have already been remarked. 
From the earth, conlidered as a planet, and the moon as its 
Satellite, we pafs through the region of the reft of the pla- 
nets, and their fatelktes. The fimiiarity between all thefe 
bodies is fufficiently ftriking to allow us to comprehend them 
under one general definition, of bodies not luminous in them- 
felves, revolving round the fun. The great diminution of 
light, when reflected from fuch bodies, efpecially when they 
are alfo at a great diftance from the light which illuminates 
them, precludes all poflibility of following them a great way 
into fpace. But if we did not know that light diminilhes 
as the fquares of the diftances encreafe, and that moreover in 
■every reflection a very confiderable part is intirely loft, the 
motion of comets, whereby the fpace through which they run is 
meafured out to us, while on their return from the fun we fee 
them gradually difappear as they advance towards their aphe- 
lia, would be fufficient to convince us that bodies Alining only 
with borrowed light can never be feen at any very great 
diftance. This confideration brings us back to the fun, as a 
refulgent fountain of light, whilft it eftablifties at the fame 
time beyond a doubt that every ftar muft likewife be a fun, 
Vql. LXXIX. K k ‘ fhin- 
