of ascertaining the Magnitude of small celestial Bodies. 47 
( 7. ) This shows that the spurious terrestrial disks, in this 
respect again resemble those of the stars; increasing when 
the aperture is lessened, and decreasing when it is enlarged. 
1 gth Experiment. 
With the same magnifying power 432,3, but a change of 
aperture, I viewed two equal globules, and two unequal ones. 
With the inside rays the equal globules were 1 diameter 
asunder. 
With all the mirror open, they were l-f- diameter asunder. 
And with the outside rays they were 2 diameters asunder. 
The unequal globules, with the inside rays, were a little 
unequal, and 1 diameter of the large one asunder. 
With the outside rays they were considerably unequal, and 
2 diameters of the large one asunder. 
( 8. ) By these experiments it is proved, that the increase 
and decrease of the diameters occasioned by different apertures 
is not proportional to the diameters of the spurious disks. 
(9.) But that the change of the apertures acts more on the 
small, and less on the large ones. 
14 th Experiment. 
No. 1 of a set of globules, has the largest spurious diameter. 
No. 3 is larger than No. 2 ; whereas No. 2 has the largest real 
diameter. It is inclined to a greenish colour. No. 3 is now 
reddish, and is larger than No. 1, which is at present less than 
No. 2. No. 1 grows bigger, and is now the largest. 
The sun which had been shining, was obscured by some 
clouds, but the spurious diameters of the globules I was viewing 
