Note 91 — MISCELLANEOUS OBSERVATIONS.

This position has been already laid down in chapter cxxiv. (and will also be found in chapter cccxlviii.); and the reader is referred to the note on that passage, which will also explain that in the text, for further illustration. It may, however, be proper to remark, that though the author has here supposed both objects conveyed to the eye by an angle of the same extent, they cannot, in fact, be so seen, unless one eye be shut; and the reason is this: if viewed with both eyes, there will be two points of sight, one in the centre of each eye; and the rays from each of these to the objects must of course be different, and will consequently form different angles.