230 Dr. Herschei/s Observations on 
Continent, to form an association for the examination of the 
zodiac. I hope they will extend their attention, by degrees, to 
every part of the heavens; and that the honourable distinction 
which is justly due to the successful investigators of nature, 
will induce many to join in the meritorious pursuit. As the 
new method of observing the zodiac has already produced such 
interesting discoveries, we have reason to believe that a number 
of asteroids may remain concealed ; for, how improbable it would 
be, that if there were but two, they should have been so near 
together as almost to force themselves to our notice. But a 
more extended consideration adds to the probability that many 
of them may soon be discovered. It is well known that the 
Comas and tails of comets gradually increase in their approach 
to the sun, and contract again when they retire into the distant 
regions of space. Hence we have reason to expect, that when 
comets have been a considerable time in retirement, their comas 
may subside, if not intirely, at least sufficiently to make them 
assume the resemblance of stars ; that is, to become asteroids, 
in which state we have a good chance to detect them. It is true 
that comets soon grow so faint, in retiring from their perihelia, 
that we lose sight of them ; but, if their comas, which are ge- 
nerally of great extent, should be compressed into a space so 
small as the diameters of our two asteroids, we can hardly 
entertain a doubt but that they would again become visible 
with good telescopes. Now’, should we see a comet in its aphe- 
lion, under the conditions here pointed out, and that there are 
many which may be in such situations, we have the greatest 
inducements to believe, it would be a favourable circumstance 
to lead us to a more perfect knowledge of the nature of comets 
and their orbits ; for instance, the comet of the year 1770, which 
