24 Dr. Goring on False Light 
manner, thatis to say, without stops in the course of the focal dis- 
tance of the object glass, or at least without effectual ones?) It 
cannot be asserted, that there is anything equivalent in the instru- 
ment in its present condition, to the former provision in it, for the 
valuable purpose of excluding false rays, though the expediency 
and utility of it in both cases, must be equally admitted or denied, 
and it is clear this can only be supplied in the astronomical teles- 
cope, by some such expedients as I haye resorted to. 
As I conceive no one can be hardy enough to assert~that there 
is no use in excluding false rays from a telescope intended to be 
used at night, for viewing the heavens, it will be superfluous for 
me, to set about proving that we shall see a celestial object the 
better, if no light, either direct or reflected, reaches the eye, save 
that actually proceeding from it. If the light of the heavens in a 
star-light night, and that of the bodies which produce it are very 
faint, still there is the same ratio between their brightness, and the 
false light they produce, (though not so conspicuous perhaps) as 
there is in that of terrestrial objects. Indeed it is perfectly well 
known to astronomers, that in the darkest night, wearing a black 
hood over the eyes, greatly facilitates the vision of very faint and 
delicate objects, such as nebule, &c., from the sensibility and tran= 
quillity induced by these means in the retina, rendering it sus- 
ceptible of the slightest impressions. Surely the effect of foreign 
light reaching the eye directly, or through the medium of a 
telescope, must be equally pernicious. It is in viewing the class 
of objects here designated, that the utility of the stops I have 
described will be found; no one will expect that they can render a 
telescope better able to define or divide a star, because these pro-= 
perties depend upon the perfection of an entirely different part of 
its structure. I shall take my leave of the subject, by asserting 
that if any one should choose to maintain a contrary opinion from 
myself on the affair of excluding false rays, he must, to preserve 
consistency, assert that there is no use in the eye-hole of the Gre- 
gorian and Cassagrain telescope, (if used at night,) and should 
therefore in using these instruments, content himself with such a 
one as is applied to common spy glasses, just to keep his eye in the 
axis of his instrument, ' 
