6 2 Dr. Herschei/s Experiments on the Means 
requires a distinct magnifying power of 5 or 6 hundred, and 
must be sufficiently bright to bear that power. 
( 3. ) A real disk of half a second in diameter will become 
so much larger by the application of a magnifying power of 5 
or 6 hundred, that it will be easity distinguished from an equal 
spurious one, the latter not being affected by power in the 
same proportion as the former. 
( 4. ) The different effects of the inside and outside rays 
of a mirror, with regard to the appearance of a disk, are a 
criterion that will show whether it is real or spurious, provided 
its diameter is more than £ of a second. 
( 5 • ) When disks, either spurious or real, are less than £ of 
a second in diameter, they cannot be distinguished from each 
other ; because the magnifying power will not be sufficient to 
make them appear round and well defined. 
( 6 . ) The same kind of experiments are applicable to tele- 
scopes of different sorts and sizes, but will give a different 
result for the quantity which has been stated at £ of a second 
of a degree. This will be more when the instrument is less 
perfect, and less when it is more so. It will also differ even 
with the same instrument, according to the clearness of the 
air, the condition, and adjustment of the mirrors, and the 
practical habits of the observer. 
With regard to Mr. Harding’s new starry celestial body, 
we have shown, by observation, that it resembles, in every 
respect, the two other lately discovered ones of Mr. Piazzi 
and Dr. Olbers ; so that Ceres, Pallas, and Juno, are certainly 
three individuals of the same species. 
