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obviate it by applying to an eminent optician to make him a 
pair of glasses with bi-focal lenses. After some delay Mr* 
Atkinson was informed by this gentleman that the thing could 
not be done ; that the only way for making a spectacle glass 
to meet the defect complained of, was to cut a convex and a 
concave lens, each of the proper focus, and to put them edge 
to edge in the frame, so as to have the convex part below and 
the concave part above. His arguments to the contrary, on 
the plea of “ ne sutor supra crepidam,” not being listened to, 
Mr. Atkinson was obliged to adopt spectacles of the kind 
recommended. These glasses answered their intended purpose 
very well, so far as to seeing botli near and distant objects, 
but besides having an unsightly bar directly across the centre 
of each glass, they were very liable to accident from falling 
out of the frame. 
A few months ago, having seen a gentleman with a pair of 
spectacles with bi-focal glasses, Mr. Atkinson ascertained the 
name of the optician who made them, and applied to him to 
have a pair made of a similar kind. He was told that the 
glasses alluded to were composed of two convex ones of 
different focal lengths — a kind that could easily be made ; 
but that a convex and a concave lens could not be made as 
required on the same piece, and that the only method of making 
spectacles of the peculiar kind he wanted was that which he 
had already had recourse to. Being still satisfied that this 
representation was incorrect, Mr. Atkinson succeeded in 
inducing the optician in question to listen to his suggestions 
for effecting the object he had in view. 
The plan suggested will be best understood by reference 
to the accompanying diagram, in which A CBD represents 
a circular piece of glass sufficiently large to admit of two 
spectacle glasses being cut out of it. This, in the first place, 
is to be ground into a plano-convex lens of the required 
focus ; then in the centre of this is to be ground a concave 
lens of the right focus, as represented by the inner circle v p. 
