576 THE SENSES AND SENSORY ORGANS. 
creased in the same ratio with that of the subcorneal image 
by increasing the effective angular aperture of the corneal 
lens. 
The actual illumination of the retinal image will then vary 
inversely as the magnifying power or the square of the linear 
magnification (m) of the second image as compared with the 
first, and directly as the intensity of the illumination of the 
first image, which increases with the surface of the corneal 
lens, and the angular aperture of the second lens. 
The surface of the corneal lens is generally very large as 
compared with the surface (a) cut by the axial pencil (// PY); let 
it be equal to A. Then the illumination of every point of the 
subcorneal image will be equal A I, and of the retinal image 
A 
t = 
oe 
: which will evidently be very large in comparison to a 
distributed over the whole surface (a), since A is usually greater 
than m?, or, in other words, the waves of light are concentrated 
by the lens systems. 
In the above the reflection or absorption of light at the 
refractive surfaces and in the media has been neglected, but 
this is immaterial to the argument. 
It appears, therefore, that the presence of a corneal lens can 
only aid vision when an image actually falls upon a recipient 
structure, and as it can be shown that no such structure exists 
in the position of Gottsche’s image, the inference is that a 
second refraction must occur beyond the image, and that a 
second real image is formed, the existence of which has 
been demonstrated by Exner’s photograph. 
To suppose that a retinal image can be produced by the 
divergent pencils beyond the focal plane of Gottsche’s image 
without a second image being formed is as inconceivable as 
that a pin-hole camera would form a picture if a small convex 
lens were added at the pin-hole and the receptive surface were 
at a distance behind it equal to many times the length of the 
principal focus of this lens. 
