Dr. Herschei/s Observations on 
21 4 
than planetary, will possibly throw also considerable light upon 
the circumstances belonging to the other celestial body ; and, 
by that means, enable us to form some judgment of the nature 
of both the two last-discovered phenomena. 
As the measures I have taken will oblige me to give a result 
which must appear extraordinary, it will be highly necessary 
to be particular in the circumstances of these measures, and to 
mention the condition and powers of the telescopes that were 
used to obtain them. 
Magnitude of the new Stars . 
April 1, 1802. Having placed a lucid disk at a considerable 
distance from the eye, but so that I might view it with perfect 
distinctness, I threw the image of Mr. Piazzi's star, seen in a 
y-feet reflector, very near it, in order to have the projected 
picture of the star and the lucid disk side by side, that I might 
ascertain their comparative magnitudes. I soon perceived that 
the length of my garden would not allow me to remove the 
disk-micrometer, which must be placed at right angles to the 
telescope, far enough to make it appear no larger than the star ; 
and, not having disks of a less diameter prepared, I placed the 
smallest I had, as far from me as the situation of the star would 
allow. Then, bringing its image again by the side of the disk, 
and viewing, at the same time, with one eye tne magnified star, 
while the other eye saw the lucid disk, I perceived that Ceies, 
which is the name the discoverer has given to the star, was 
hardly more than one third of the diameter of the disk, and 
certainly less than one half of it. 
This being repeated, and always appearing the same, we 
