272 Dr. Herschei/s Astronomical Observations 
times, could not be so particularly and comprehensively de- 
tailed in the confined space of the catalogues as I now may 
describe them ; additional observations have also now and 
then given me a better view of the objects than I had before. 
This remark will always apply to the numbers which refer to 
the Connoissance des Temps; for the nebulae and clusters of 
stars are there so imperfectly described, that my own obser- 
vation of them with large instruments may well be supposed 
to differ entirely from what is said of them. But if any astro- 
nomer should review them, with such high space-penetrating- 
powers, as are absolutely required, it will be found that I have 
classed them very properly. 
It will be necessary to mention that the nebulous delinea- 
tions in the figures are not intended to represent any of the 
individuals of the objects which are described otherwise than 
in the circumstances which are common to the nebulas of each 
assortment : the irregularity of a figure, for instance, must 
stand for every other irregularity; and the delineated size for 
every other size. It will however be seen, that in the figure 
referred to there is a sufficient resemblance to the described 
nebula to show the essential features of shape and brightness 
then under consideration, 
1 . Of extensive diffused Nebulosity. 
The first article of my series will begin with extensive dif- 
fused nebulosity, which is a phenomenon that hitherto has not 
been much noticed, and can indeed only be perceived by in- 
struments that collect a great quantity of light. Its existence, 
when some part of it is pointed out by objects that are within 
the reach of common telescopes, has nevertheless obtruded 
