44 D/\ Herschel’s Experiments on the Means 
Oct. 12, 1782. I tried a new plain speculum, made by a very 
good workman, and found that when I viewed a Geminorum 
with 460, the vacancy between the two stars was barely \\ 
diameter, but the same telescope and power with my own 
small speculum, made the distance 2 diameters, so that the 
figure of this mirror affects the spurious diameters of the stars. 
(11.) Hence we may conclude that many causes will have 
an influence on the apparent diameter of the spurious disks of 
the stars ; but they are so far within the reach of our know- 
ledge, that with a proper regard to them, the conclusion we 
have drawn in Rem. ( 2. ) “ that under the same circumstances 
“ their dimensions are permanent/’ will still remain good. 
SPURIOUS DIAMETERS OF TERRESTRIAL OBJECTS, WITH SIMILAR 
REMARKS. 
7 th Experiment with Silver Globules. 
A number of silver globules were put on the post, before 
they had been tarnished ; and the sun shone upon them. When 
I viewed them in the telescope, there was on each of them a 
lucid appearance resembling the spurious disk of a star. I 
could distinguish this bright spot from the real diameters of 
the globules perfectly well, and found it much less than they 
were. 
Rem. (1.) Hence we conclude that the terrestrial, spurious 
disks of globules are less than the real disks ; whereas we 
have seen, in Remark (1.) of the celestial spurious disks, that 
these are larger than the real ones. 
