A. G. Mayer — Improved Ileliostat. 



307 





The common forms of heliostats consist of one or more 

 plane mirrors carried by a driving clock so as to maintain a 

 solar beam continuously in one direction. The plane mirrors 

 have to be of considerable size, and for accurate work are 

 costly, moreover it is a matter of much difficulty to insure a 

 constant direction of the reflected light owing to the com- 

 plexity of the mechanism of the driving apparatus. 



The heliostat here described avoids these difficulties, is of 

 very simple and cheap construction and possesses the unique 

 advantage that it will maintain a parallel, convergent, or 

 divergent solar beam in one direction with perfect steadiness, 

 and will produce a highly illuminated field of uniform intens- 

 ity with an amount of heat much less than that given by the 

 forms of heliostats hitherto used. 



The essential and characteristic parts of the instrument 

 (fig. 2) consist in a biconvex lens (J) which receives the sun's 

 light and produces a convergent beam that is rendered parallel 

 by the small biconcave lens (K). The beam is then reflected 

 in some desired direction by means of the totally reflecting 

 prism (f). The two lenses, J and K, and the prism,/, are all 



