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Transactions of the Society. 
debatable projection distances which have caused so much argument 
in a circle, and unnecessary confusion of ideas. Let it be understood 
that when we speak of normal sight we mean a sight possessing a 
range of accommodating power for distances of 8 in. to oo , and when 
of myopic sight for distances of 4 in. to 8 in. The following six 
examples will illustrate the subject : — 
(1) If an object 1/2 in. long is placed 8 in. in front of a normal 
eye, the image of that object on the retina will be • 03 1 in. 
(2) A myopic person, however, would hold the object 4 in. from 
the eye, and the image on the retina would he *062 in. long. 
(3) If the normal eye used a lens 1 in. in focus, the eye being 
placed at the posterior focal point, the image on the retina would be 
enlarged to '248 in, or eight times more than in example (1), which 
enlargement, according to our definition, will represent the magnifying 
power. 
(4) The myopic eye under similar conditions will have a retinal 
image of ’248 in., or the same as with the normal eye; the mag- 
nifying power, however, will be only 4 times, the image on the myopic 
retina without the lens being twice the size of that on the normal 
retina. 
If in these last two cases the power is actually measured by super- 
imposing the magnified image seen by one eye on the unmagnified 
image seen by the other eye, the results will agree with the above. 
(5) If the normal eye is placed close to the lens, the image on the 
retina will be '279 in., or 9 times larger than in case (1) without 
the lens. 
(6) If the myopic eye is placed close to the lens, the image on the 
retina will be equal to ‘31 in., or 5 times larger than without the lens. 
Hence it appears that, although in this last example the magni- 
fying power is not so great as in example (5), the retinal image is 
somewhat larger. 
By confining the argument to retinal images the discussion is, as 
we said above, much simplified, and we are enabled to see clearly that, 
although the resultant virtual image, so long as the eye is held at the 
posterior focal point of the lens, is the same size whether the eye is 
normal or myopic, the magnifying power is different. 
Abbe, however, states that “ The amplifying power of every system 
is always the same for both, because the image is seen under the same 
visual angle.” 
The following very important example can only he explained by 
my hypothesis : — Before giving the example, let me point out that 
any normal sighted person can make himself myopic by the use of a 
convex spectacle lens. Thus, if a normal sighted eye, whose least 
distance of accommodation is 8 in., uses a convex spectacle lens of 8 in. 
focus, the eye will be made similar to a myopic eye, whose least 
accommodating distance is 4 in. ; so any of these examples can be 
performed by normal sighted persons. The important example is as 
