448 eepokt — 1878. 



MONDAY, AUGUST 19, 1878. 



A Department of Mathematics was constituted. — See p. 457. 



The following Papers were read in the General Section : — 



1 . Report of the Committee on Atmospheric Electricity. 

 See Reports, p. 103. 



2. On Edmunds' Electrical Phonoscope. By W. Ladd. 



An instrument for producing figures of light from vibrations of sound. It 

 consists essentially of three parts — an induction coil, an interrupter, and a rotary 

 vacuum tube. 



The action of the instrument is as follows : — Sounds from the voice or other 

 sources produce vibrations on the diaphragm of the interrupter, which being in 

 the primary circuit of the induction coil, induce at each interruption a current in 

 the secondary coil similar to the action of a contact-breaker or rheotome. There- 

 fore each vibration is made visible as a flash in the vacuum tube. The tube 

 revolving all the time at a constant speed, the flashes produce a symmetrical figure 

 as the spokes of a wheel, or as in the Gassiot star. The number of spokes or radii 

 are according to the number of vibrations in the interrupter during a revolution of 

 the tube, and the number of vibrations being varied to any extent according to the 

 sounds produced, the figures in the revolving tube will be varied accordingly. The 

 same sounds always produce the same figures, providing the revolution be constant. 

 In case of rhythmical interruptions being produced in a given sound, as in a trill, 

 most beautiful effects are noticeable, owing to the omission of certain radii in 

 regular positions in the figure. 



The uses of this instrument are the rendering visible of sounds, and showing 

 the vibrations required in their production, and is a mode of confirming by sight an 

 appeal to the ear. 



3. On Byrne's Compound Plate Pneumatic Battery. By W. Ladd. 



This battery is the invention of Dr. Byrne, of Brooklyn, U.S. A. The chief features 

 in this battery are a compound negative plate, and a simple mechanical means for 

 preventing polarisation. The negative plate consists of the extreme negative 

 element platinum, backed up by a plate of copper to reduce the resistance ; the 

 copper being protected by a thin sheet of lead, to prevent any local action that 

 might occur owing to holes in the platinum, which would allow the exciting fluid 

 to attack the copper, and a thicker sheet of lead on the back of the copper which 

 is japanned. So a plate in section would show as consisting of, first, a sheet of 

 platinum, then thin lead, then copper, and last, the thick japanned lead, the whole 

 being soldered together to form a solid plate. 



The batteries are built up with a zinc plate and two of the compound plates ; 

 the exciting fluid being a bichromate of potash and dilute sulphuric acid solution. 



This battery would soon become polarised but for the injection of air between 

 the plates, which action appears simply mechanical and not chemical, various gases 

 producing no different effects. 



"When the air is pumped in, the most extraordinary effects may be produced, 

 the " quantity " being much more than that of any other battery of the same size. 



