308 A. G. Mayer — Improved Heliostat. 



arranged upon a common axis, and mounted equatorially in a 

 suitable frame-work adjustable to the sun's declination by 

 means of the graduated arc (S, fig. 1). This frame work is 

 controlled by a driving clock (A, fig. 1) of the type commonly 

 used in other heliostats. The beam of light which is reflected 

 from the prism (f) may be thrown in any direction by means 

 of the reflecting prism, L (fig. 2), which is placed somewhere 

 near but forms no essential part of the instrument. 



This heliostat is especially well adapted to microscopic and 

 spectroscopic work and to projection with the lantern. By its 

 means a very intense beam of sunlight may be obtained, which 

 is so remarkably free from heat that it may be passed with 

 perfect safety through microscopic slides containing the most 

 delicate objects. In this manner beautifully well-defined 

 images of microscopic objects were thrown upon a screen 

 under a magnification of 3800 diameters. 



Harvard University, August 1st, 1897. 



