No. 53835. 



Mirror Sextants. Reflection. Refraction. 



483 



53 828. 1 : 5. 



53 833. 1 : 7. 



53 829. 1 : 4. 



53 830. 1 : 4. 



53 832. 1 : 2. 



53 835. 1 : 6. 



53.829. Mirror Sextant, Figure, entirely of brass, with telescope and 4 screening glasses, 

 the vernier giving 5 minutes 



53.830. Mirror Sextant, Figure, Large Pattern, entirely of brass, with circle divided on 

 silver, witli telescope, screening glasses, vernier with magnifying glass 



53.831. Level Quadrant, for determining angles of altitude to an accuracy of 1 minute . . 



The level and the object are observed simultaneously in the telescope. The instruments can also 

 be used on vehicles, ships, airships, etc. 



53,832. Pocket Heliotrope after Steinheil, Figure, in case . 

 The apparatus gives luminous signals to a distance of 50 km. 



Refraction, Total Reflection. 



33,833. Light-Refraction Apparatus, after Miiller, Figure, for showing the refraction of light- 

 rays in liquids, with etched graduation on ground glass, metal vessel with gap . . . 



53.834. - - idem, entirely of glass 



53.835. Light-Refraction Apparatus after Miihlenbein, Figure, for demonstrating the 

 laws of reflection and of refraction for solids and liquids; also total reflection; can also 

 he used as a camera obscura (Prakt. Phys., Vol. 2, Part 1) 



The apparatus lias circular and sine graduation, and has, as accessories, a Plane Mirror, two 

 Half -cylinders of crown and flint glass respectively, also a hollow cylinder for liquids. 



. s. d. 

 4. 10. 



10.10. 

 3. 15. 



4. 0. 



0. 16. 

 0. 12. 



8. 0.0 



Heliographs for Signalling Particulars on Application. 



Cl. 1257, 5299, 6041, 



1259, 1261, 1296. 31* 



