34 Dr. Herschel’s Experiments on the Means 
the art of making them perfectly round and extremely small. 
To prevent my seeing them at a distance in a different aspect 
from that in which they were measured under the microscope, 
I fixed the needles with sealing-wax on small slips of cards 
before the measures were taken. 
Eight of these globules of the following dimensions ,04,66 
,0325 ,0290 ,02194 ,0210 ,0169 ,0144 ,00763 were placed 
upon the post in my garden, and I viewed them in the telescope. 
With a power of 231,8 I saw all the first seven numbers 
well defined, and round, and could see their gradual decrease 
very precisely from No. 1 to No. 7. 
With 303,5 I saw them better, and had a glimpse of No. 8, 
but could not be sure that I saw it distinctly round ; though 
the magnified angle was 3' 18", 2. 
With 432,0 they are all very palpable objects, and, as a 
solid body, No. 8 may be seen without difficulty ; at the centre 
of the mirror it subtends an angle of o",653. With attention 
we may also be sure of its roundness ; but here the magnified 
angle is not less than 4' 42", 1. 
With 522,3 I see them all in great perfection as spherical 
bodies, and the magnitude of No. 7 may be estimated in quarters 
of its diameters. The angle is i",253, and one quarter of it is 
o",3i3. No. 8 maybe divided into two halves with ease; each 
of which is o'', 327. 
With 925,4 I saw No. 8 still better ; but sealing-wax is not 
bright enough for so high a power. 
By tliis experiment it appears, that with a globule so small 
as ,00763 of a substance not reflecting much light, the mag- 
nified angle must be between 4 and 5 minutes before we can 
see it round. But it also appears that a telescope with a sufficient 
