252 
LORD brougham’s EXPERIMENTS AND OBSERVATIONS 
notoriously the case, the breadth of the fringes decreasing with their distance from 
the direct rays. 
4. In the case of the fringes formed by the second body inflecting and the first de- 
flecting, there can be no interference at all ; for the whole action is on one and the 
same pencil or beam. A deflects and thenB inflects the same ray ; and when a third 
edge is placed on the opposite side to B, it only deflects the same ray, which is thus 
twice bent further from the direct rays, the last bending increasing that distance. 
5. Let A be the first and B the second edge as before (fig. 20). Suppose B to be 
moveable, and find the equation to the disposing force at different distances of the 
two edges, we shall find this to be y— « being =AE, 6 = ED, 
and AB=j:. But all the experiments show it to be y— a wholly different curve. 
Again, let B be fixed, or the distance of the two edges be constant, we shall get the 
equation (a being =AE, Z>=BE, 5=DE 
and E C=.r) y— 
1 
V -\-{x—bY^— \/c^ + x^^ 
also a wholly different curve from the conic hyperbola, which all experiments give. 
Therefore the conclusion from the whole is that the phenomena have no reference to 
interference. 
Having delivered the doctrines resulting from these experiments, 1 have some few 
particulars to add, both as illustrating and confirming the foregoing propositions, as 
removing one or two difficulties which have occurred to others until they were met by 
facts, and also as showing the tendency of the results at which we have arrived. 
1. It may have been observed that in all these propositions I have taken for granted 
the inflexion of the rays by the body first acting upon them as well as their deflexion 
by that body, and have reasoned on that supposition. It is, however, not to be de- 
nied that we cannot easily perceive the fringes made by the single inflexion, as we 
can without any difficulty perceive those made by the single deflexion, and fully de- 
scribed in Proposition I. Sir I. Newton even assumes that no fringes are made 
within the shadow. I here purposely keep out of view the fringes made in the 
shadow of a hair or other small body, because the principle of interference there 
comes into play. However, I will now state the grounds of my assuming inflexion 
and separation of the rays by their different flexibility, when only a single body acts 
on them. In the Jirst place, the first body does act in some way ; for the second only 
acts after the first, and if the first be removed the fringes made in its shadow by the 
second at once vanish. Secondly, these fringes made by the second depend upon its 
proximity to the first. Thirdly, the following experiment seems decisive. Place 
instead of a straight edge one of the form in fig. 18, and then apply at some distance 
from it, the second edge, as in the former experiments. You find that the fringes 
assume the form, somewhat like a small tooth-comb, of a b. If the second edge is 
