50 Dr. Herschel’s Experiments on the Means 
925,4 nearly equal, and Qj diameters of the largest asunder. 
706.3 nearly equal, and above 2 diameters of the largest 
asunder. 
432.3 pretty unequal, and 2 diameters of the largest asunder. 
177,0 considerably unequal, and if diameter of the largest 
asunder. 
I examined also two other drops, with different apertures, 
without changing the power, which was 706,3. 
With the inside rays they were very little unequal, and \ 
diameter of the largest asunder. 
With the outside rays they were considerably unequal, and 
if diameter of the largest asunder. 
From what has been said, it appears that all the remarks 
which have been made with regard to the spurious disks of 
the silver globules are confirmed by the luminous spots on the 
drops of quicksilver. There is a difference in the proportion 
which the spurious disks on quicksilver bear to the drops, and 
that on the silver globules to the size of the globules ; the 
latter also give a greater variety of colours and magnitudes 
than those on quicksilver ; these are circumstances of which 
it would be easy to assign the cause, but they can be of no 
consequence to the result we have drawn from the experiment. 
1 6th Experiment, with black and white Circles. 
I tried to measure some of the spurious disks by projecting 
them on a scale with a moveable index, but found their dia- 
meters were too small for accuracy by this method; for this 
reason I had recourse to artificial measuring-disks, and pre- 
pared a set of eleven white circles on a black ground, and 
eight black ones on a white ground. In order to guard against 
