2 2 Mr. herschel on the 
does not appear. Theories are only to be ufed when proper 
data are afligned ; but the data are carefully to be re-examined, 
when new improvements may widely alter therefult of former 
experiments. Thus, we are told, that we gain nothing by 
magnifying too much. 1 grant it; but fhall never believe I 
magnify too much till by experience I find, that 1 can fee better 
with a lower power. Nor is even that fufficient : a lower 
power may fhew more of the objeft ; it may fhew it brighter, 
nay even diftincter, and therefore upon the whole better ; and 
yet the greater power may, in a particular cafe, be preferable : 
for if the object is fo fmall as not to be at all vifible with the 
lower power, and I can, by magnifying more, obtain a view of 
it, though neither fo bright nor diftinct as 1 could with, is it 
not evident, that here this power is preferable to the former ? 
The naturalift does not think himfelf obliged to account for 
all the phaenomena he may oblerve ; the aftronomer and opti- 
cian may claim the fame privilege. When we increafe the 
power we leffen the light in the inverie ratio of the fquare 
of the power; and telefcopes will, in general, difcover more 
fmall fhirs the more light they colletf: ; yet with a power 
of 227 I cannot fee the fmall ftar near the ftar following 
0 Aquilae, when, by the fame telefcope, it appears very plainly 
with the power of 460 : now, in the latter cafe, the power 
being more than double, the light is lefs than the fourth 
part of the former. In fuch particular cafes I generally fufpedi: 
my own eyes, and have recourfe to thofe of my friends. I had 
the pleafure of fhewing this ftar to Dr. watson junior, who 
foon difcovered the fmall ftar, which accompanies the other, 
with the power of 460; but faw nothing of it with 227, 
though the place where to look for it had been pointed out to 
him by the higher power. The experiment has been too often 
repeated 
