Some new direct vision dispersion prism systems.

Direct vision prisms are useful for quick examination of any spectrum. Most of the commercial direct vision instruments utilize the cemented type Amici prism consisting of both crown and flint prisms. In this paper a type of direct vision prism made of single glass is discussed. It utilizes two refractions for dispersive purposes and an even number of internal reflections. In addition some other types of direct vision prisms are described differing from the usual Amici type.