previous next

Tein′o-scope.

A name given by Sir David Brewster to the prism-telescope.

If a prism be placed horizontally with the refracting edge downward, so that the visual rays from an object enter and emerge from it at equal angles, the object will appear of its natural size; if the refracting edge be turned toward the object, this will appear to be elongated or magnified vertically. A similar prism placed vertically magnifies the object in the direction of its width; and a combination of the two gives an image enlarged in both directions, but fringed with the prismatic colors. This may be corrected by making the prisms of a glass which only transmits one color; by viewing the fringed image through a piece of glass of this kind; or, what is better for most purposes, by using a second pair of similar prisms placed in reversed directions to the first.

Professor Amici, of Modena, used a combination of four rectangular prisms, having their refracting angles different and connected in pairs; the pair nearest the edge are vertical, and the second pair horizontal, so as to produce equal refraction in each direction, the magnifying power being about three times. This plan is well adapted for ordinary glasses.

Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 United States License.

An XML version of this text is available for download, with the additional restriction that you offer Perseus any modifications you make. Perseus provides credit for all accepted changes, storing new additions in a versioning system.

hide Places (automatically extracted)

View a map of the most frequently mentioned places in this document.

Download Pleiades ancient places geospacial dataset for this text.

hide People (automatically extracted)
Sort people alphabetically, as they appear on the page, by frequency
Click on a person to search for him/her in this document.
David Brewster (1)
Amici (1)
hide Display Preferences
Greek Display:
Arabic Display:
View by Default:
Browse Bar: