374 Mr. Brougham’s Experiments and Observations 
emerged from it well coloured, and in regular order, with their 
dark intervals. This may easily be tried by candle-light with 
a piece of looking-glass, and those who without much trouble 
would satisfy themselves of the truth of the whole experiment 
contained in this and the last observation, may easily do it in 
this way with a concave speculum ; but the beauty of the ap- 
pearance is hereby quite impaired. After this detail it is almost 
superfluous to add, that the fringes at B, fig. 6 . are formed by 
deflexion from the edge of the speculum next the sun, and then 
falling on it are reflected to the chart; that the images by re- 
flexion are either formed by the light being decompounded at 
its first reflexion, and then undergoing a second, or, in other 
instances, without this second reflexion ; and that the other 
fringes are produced exactly as described above, from the ne- 
cessary consequences of the theory. I shall only add, that 
nothing could have been more pleasing to me than the success 
of this experiment ; not only because in itself it was really beau- 
tiful from its variety, but also because it was the most peremp- 
tory confirmation of what followed from the theory a priori , 
and in that point where the singularity of its consequences 
most inclined me to doubt its truth. 
Let us now attend to several conclusions to which the fore- 
going observations lead, independently of the propositions (viz. 
the five first) which they were made to examine. 
J. We must be immediately struck with the extreme resem- 
blance between the rings surrounding the black spots on the 
image made by an ill polished speculum, and those produced 
by thin plates observed by Newton ; but perhaps the resem- 
blance is still more conspicuous in the colours surrounding the 
image made by any speculum whatever, and fully described in 
