212 SEC. 7. LIGHT. 



VIII. EDUCATIONAL. 



963. Two Frames with 126 Photographs on Glass, for 



projection by the lantern, for instruction in the natural sciences. 



Romain Talbot, Berlin. 



964. Pour simple Models, for instruction in the use of the 



telescope and the microscope. 



J, Wilhelm Albert, Frankfort- on- Maine. 



The four models for optical instruction are open instruments with lenses 

 and shades. They show the course of the rays and illustrate in a simple 

 manner the Galilean, astronomical, and terrestrial telescopes, and the com- 

 pound microscope. 



These models are largely used in German and foreign educational insti- 

 tutions. 



965. Coloured Chalks for lectures, with a Black Board. 



C. Blattner, Munich. 



966. Interference Apparatus by Fresnel, executed for edu- 

 cational purposes by Ch. Jung, Giessen. 



Physical Collection of the University of Giessen ; Pro- 

 fessor Buff. 



967. Handy Educational Apparatus, for fundamental expe- 

 riments on Refraction. 



Professor Dr. J. J. Oppel, Frankf or t-on- Maine. 



This apparatus is only a modification of the old experiment of viewing 

 a coin at the bottom of a basin full of water. The coin is replaced by a white 

 line upon black ground, and the water through a movable cube of glass. 

 The position of the eye is fixed by a dioptric plate. 



968. Handy contrivance for illustrating astronomical 

 refraction and its effect on measured heights of stars. 



Professor Dr. J. J. Oppel, Frankfort-on- Maine. 



The eye looks through a dioptric plate over a wooden globe (" earth ") 

 towards a few stars and the rising moon, which appears above or below the 

 horizon, according as the piece of glass, which represents the refracting 

 atmosphere, is lifted up or removed by means of a contrivance attached to it. 



969. Two Colour-tables, for illustrating " colour blindness/' 

 with greenish glass (absorbing the ends of the spectrum) belonging 

 to them. Professor Dr. J. J. Oppel, Frankfort-on- Maine. 



Both tables, each with 10-12 colour-couples upon black ground, have 

 references to the most frequent form of achromatopsy, the so-called red, 

 respectively green, blindness. The one table contains col our- couples which 

 are most generally mistaken for one another ; the other such that are never 

 mistaken. The green glass, added to the tables, enables a normal eye to get 

 an idea of the correctness of the preceding statements. 



