Rensselaer Semi-Weekly Republican, Volume 37, Number 7, Rensselaer, Jasper County, 27 January 1905 — Peculfarities of Eyes. [ARTICLE]

Peculfarities of Eyes.

bmnan eye In perfect condition to able to see objects separately that a** only one minute of arc apart. Put tw° Objects—as, for instance, two black fcfrfcles on a white ground—just one Inch apart and then'place them at a distance of about 2SGI4 feet. As seen with the naked eye the apparent space between the circles will be a iniDute of arc. This space is plainly the limit of detail visible*to the unassisted human eye. Now, it might be supposed that an Insect, having a compound eye, would be able to see more detail than we can do—in other words, could separate small objects closer Together. As a matter of fact, owing to the small aperture of the lenses composing the facets of the eye and the spacing between the facets, insects see less detail than we do. Dr. G. Johnstone Stoney calculated that a dragon fly cannot sec separately two objects which are placed less than one degree apart. In other words, to such ah insect two silver coins lying on a table three Inches apart and viewed from a distance exceeding fourteen and one-third feet would appear as a single object. Bees and flies, according to the same authority, are still more limited in their ability to see the details of objects presented to their eyes. A fly cquld only see the two silver coins above described separately at a distance not exceeding about seven sept.