274 £>c. Herscehl’s Astronomical Observations 
has been in the dark long enough for the eye to recover from 
the impression of having been in the light. 
I have collected fifty-two such observations into a table, 
and have arranged them in the order of right ascension. In 
the first column they are numbered ; in the second and third 
columns are the right ascension and north polar distance of 
a place which is the central point of a parallelogram compre- 
hending the space which the nebulosity was observed to fill. 
They are calculated for the year 1800. 
The length and breadth of the parallelograms are set down 
in the 4th and 5th columns in degrees and minutes of a great 
circle. The time taken up in the transit of each parallelogram 
having been properly reduced to space by the polar distance 
given in the 3d column, in order to make it agree with the 
space contained in the breadth of the zone described by the 
telescope ; the dimensions of the former space therefore is in 
the parallel, and that of the latter in the meridian. My field 
of view, being fifteen minutes in diameter, its extent has been 
properly considered in the assigned dimensions of the paral- 
lelograms. It is however evident that the limits of the sweep- 
ing zone leave the extent of the nebulosity in the meridian 
unascertained. The beginning of it is equally uncertain, since 
the nebulous state of the heavens could only be noticed when 
its appearance became remarkable enough to attract attention. 
The ending is always left undetermined ; for, as the right 
ascension was only taken once, I have allowed but a single 
minute of time for the extent of the nebulosity in that direc- 
tion, except where the time was repeatedly taken with a view 
to ascertain how far it went in the parallel ; or when the cir- 
cumstances of its brightness pointed out a longer duration. 
