Every shaded body that is larger than the pupil and that interposes
between the luminous body and the eye will be seen dark.

When the eye is placed between the luminous body and the objects
illuminated by it, these objects will be seen without any shadow.

[Footnote: The diagram which in the original stands above line 1 is
given on Plate II, No 2. Then, after a blank space of about eight
lines, the diagram Plate II No 3 is placed in the original. There is
no explanation of it beyond the one line written under it.]