TEACHING APPARATUS. 1025 



10. For illustrating the production of Vocal Sounds. 



Wooden funnel, with stretched membrane. 



11. Diagrams. 



(.) Interference of sound. 



(b.) Section of organ pipe. 



(c.} Formation of nodes on a string. 



(d.) Human ear. 



(e.) Human larynx. 



Matthew William Dunscombe, Bristol. 



4091. Teacher's Portable Lecture Set for demonstrating 

 the principles of the science of Light, comprising the following 

 apparatus : 



1. For demonstrating the Velocity of Propagation. 



Movable diagram showing Roemer's observation. 



2. For demonstrating the Undulatory Theory. 



Model showing propagation of wave by series of rotating 

 particles. The difference between the vibrations of 

 waves of light and sound is shown by the production 

 of both simultaneously in close proximity. 



3. For demonstrating the Law of Inverse Squares and Relative 

 Intensities of Lights. 



Two square frames, one four times the area of the other, 

 fitted at the corners to four wires, representing rays of 

 light diverging from a point ; Wheatstonc's photometer, 

 a new and highly improved form ; discs of paper in 

 frame with oiled spot for Bunsen's method. 



4. For demonstrating the Laws of Reflection : 

 (a.) By plane mirrors. 



Plane mirror and candle ; pair of mirrors fringed for 

 showing principle of kaleidoscope ; movable model 

 (quite new), showing law of angular velocity in ray 

 reflected by rotating mirror. 

 (b.) By curved mirrors : 



Convex and concave silvered glass mirrors, carefully 

 worked ; semi-cylindrical mirror to show caustic curves ; 

 three movable models illustrating the properties of the 

 foregoing. 



5. For demonstrating the Laws of Refraction : 

 (a.) At plane surfaces. 



Equi -angular glass prism on jointed pillar; disc painted 

 with lines showing paths of incident and refracted rays, 

 for immersion up to the centre in water; movable 

 models to show the law of lines and passage of a ray 

 through a sheet of glass with parallel faces ; right-angled 

 lass prism on pillar, to show total internal reflection. 

 hree-inch diameter double convex lens on pillar and 

 40075. 3 T 



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