f*a Mr. Schroeter’s new Observations 
decrease of light toward the boundary of illumination , which itself 
was not sharply defined. 
It is right that every acute observer should be on his 
guard against a precipitation which often occurs, and not con- 
tradict respectable astronomers who have preceded him, if 
he should not at once, in a few observations, find those ap- 
pearances in an object which such credible men have per- 
ceived, or deduced from their observations. The [mischief 
thence arising may be important, and lead to more general 
error in proportion to the celebrity of the contradicting ob- 
server, because there are always persons enow who will adopt 
it as a truth without further examination. And yet there are 
many examples of this in the most modern history of astro- 
nomy. Thus, for instance, the old worthy selenographer 
Hevelius found some of the mountains of the moon to be 
more than J of a (German) geographical mile in perpendicular 
height; and this truth stood more than 100 years in all the 
elementary books. Later astronomers measured only a few 
of those mountains, and partly not with all the requisite cir- 
cumspection; yet concluded, from too few and insufficient 
observations, that Hevelius had given them much too high.* 
This was already received as true in the elementary books ; 
notwithstanding which the excellent Hevelius was absolutely 
in the right, as is proved by my numerous and incontrovertible 
measurements. -f 
When, in the years 1789 and 1790, the ring of Saturn ap- 
peared as a straight line of light, I perceived only a few pro- 
* See Roslers Handbucb der practischen Astronomic, 1 Th. p. 441. — Philos. 
Trans. Vol. LXX. 
f Selenograpbiscbe Fragmente, § 34 to 82. 
