2'5o Dr. Maskelyne’s Attempt to explain 
Moreover, Sir Isaac Newton hasobferved, with refpeft to 
the like difficulty of accounting for the diftindtnefs with which 
refracting telefcopes reprefent objeCts, that the erring rays are 
not fcattered uniformly over the circle of diffipation in the 
focus of the obje£t-glaf$, but collected infinitely more denfely 
In the center than in any other part of the circle, and in the 
way from the center to the circumference grow continually 
rarer and rarer, fo as at the circumference to become infinitely 
rare ; and by reafon of their rarity are not ftrong enough to be 
vifible, unlefs in the center and very near it. 
He farther obferves, that the moft luminous of the prifma- 
iic colours are the yellow and orange, which affeCt the fenfe 
more ftrcngly than all the reft together ; and next to thefe in 
ftrength are the red and green ; and that the blue, indigo, and 
violet, compared with thefe, are much darker and fainter, and 
compared with the other ftronger colours, little to be regarded ; 
and that therefore the images of the objeCts are to be placed 
not in the focus of the mean refrangible rays, which are in 
the confine of green and blue, but in the middle of the orange 
and yellow, there where the colour is moft luminous, that 
which is in the brighteft yellow, that yellow which inclines 
more to orange than to green. 
From all thefe confiderations, and by an elaborate calcula- 
tion, he infers, that though the whole breadth of the image 
of a lucid point be T x T th of the diameter of the aperture of 
the objeCt-glafs, yet the fenfible image of the fame is fcarce 
broader than a circle whofe diameter is part of the dia- 
meter of the aperture of the objeCF glafs of a good telefcope ; 
and hence he accounts for the apparent diameters of the fixed 
ftars as obferved with telefcopes by aftronomers, although in 
reality they are but points. 
The 
