s8o Dr. Herschel’s Astronomical Observations 
ceedingly great, but when we consider that its greatest bright- 
ness does not equal that of small telescopic stars, as may be 
seen by comparing four of them situated within the inclosed 
darkness of the nebula, and several within its brightest ap- 
pearance, with the intensity of the nebulous light ; it cannot be 
expected that such nebulosities will remain visible when ex- 
ceedingly farther from us than this prime nebula : the ratio 
of the known decrease of light will not admit of a great range 
of visibility within the narrow limits whereby this shining 
substance can affect the eye. 
From this argument a secondary conclusion may be drawn, 
which adds to what has already been said in the foregoing 
article, namely, that if our best telescopes cannot be expected 
to reach the nebulous matter, which by analogy we may sup- 
pose to be lodged among the very small stars plainly to be 
seen by them ; the actual quantity of its diffusion may still 
farther exceed even the vast abundance of it already proved 
to exist. A nebulous matter, diffused in such exuberance 
throughout the regions of space, must surely draw our atten- 
tion to the purpose for which it probably may exist ; and it 
must be the business of a critical inquirer to attend to all the 
appearances under which it will be exposed to his view in the 
following observations. 
4. Of detached Nebulosities. 
The nebulosities of the preceding articles are not restricted 
to an extensive diffusion ; we meet with them equally in de- 
tached collections ; I shall only mention the following six.* 
V. 21 consists of “ A broad faint nebulosity extended in the 
* See I. 92. V. 21, 26, 36, 41, 42. 
