368 Mr. Brougham's Experiments and Observations 
nermost fringe was broadest, the others decreasing in order 
from the first. I could sometimes see four of them, and when 
made at the edge of the large image, I could indistinctly dis- 
cern the lineaments of a fifth : when two of the spots were 
very near one another, their rings or fringes ran into one an- 
other, crossing. 
Observation 3. When the chart was removed to a greater 
distance, as six feet, the fringes were very distinct and large in 
proportion; also the smaller spots became more plain, and 
their rings were seen, though confusedly, from mixing with 
one another. When the speculum was turned round horizon- 
tally, so that its inclination to the incident rays might be greater, 
the distance of the chart remaining the same (by being drawn 
round in a circle), the spots and fringes evidently were dis- 
tended in breadth. I have endeavoured to exhibit the sun's 
image, as mottled with fringes or rings and spots, in fig. 5. 
Observation 4. I placed the speculum behind a screen with 
a hole in it, through which were let pass the homogeneal rays 
of the sun, separated by refraction through a prism ; this being 
turned on its axis, the rays which fell on the speculum were 
changed ; the fringes were now of that colour whose rays fell, 
and when the rays shifted, the fringes contracted or dilated, 
being broadest in the most flexible rays, and consequently in 
those whose flexity is greatest. 
Observation 5. The direct light falling on the speculum, and 
part of the reflected light on the horizontal white stage of a 
very accurate micrometer, I measured the breadth of the fringes, 
spots, &c. These, with the distance of the speculum from the 
window and micrometer, and the size of the sun’s image, are set 
down in the following table, all reduced to inches and decimals. 
