VIII. SPECIAL COLLECTIONS. 197 



762. Wertheim's Apparatus. 



763. Pipe with glass side, and membrane. 



764. Pipe carrying a slide, enabling holes of different sizes 

 and shapes to be opened in the same situation. 



765. Four Pipes, all containing the same mass of air, ona 

 cylindrical, one cubical, one tetrahedral, one spherical. 



766. Three Pipes containing the same mass of air, one pris- 

 matic, one in the shape of a right cone, one in that of an inverted 

 cone. 



767. Mons. Bourbouze's Pipe with glass side, bearing 

 three membranes, with mirror, one placed at the node of the first 

 sound, the two others at the two nodes of the second sound. 



768. Six Plates, five of different woods, one of brass. 



769. Two Plat Bods of brass for transverse vibrations. 

 Support for fixing these. 



7 7O. Sonometer on Mons. Barbereau's principle. 

 771. Circular Membranes, with varied tensions. 



772. Two Tuning Forks on resonance box, to give four 

 beats a second. 



773. Two Tuning Forks, mounted between the poles of 

 electromagnets, with contact-breaker. 



774. Duhamel's Vibroscope. 



775. Apparatus for transmi; 

 juids. 



776. Instrument for showing the quality of vowel-sounds. 



775. Apparatus for transmission of vibrations through 

 liquids. 



Various Scientific Instruments illustrating the Phenomena of 

 Sound, invented and made by the late John Henry Grics- 

 bacli. 



'777. Monochord, with apparatus for printing and regis- 

 tering the vibrations of strings, with a view to ascertaining the 

 number of vibrations per second. 



778. Phonometer, by means of which the equally tempered 

 12 fixed sounds in the octave may be produced. 



779. Monochord, giving the positions of the Nodal Points 

 in vibrating strings. 



