Intelligence and Miscellaneous Articles. 79 



per second, and that without solution of continuity ; (2) reproduces 

 equally ivell accords in all possible tones, varying, if it be wished, 

 in a continuous manner on the velocity of the apparatus which pro- 

 duces the intermittences being varied in a continuous manner. For 

 this purpose the apparatus is composed of a glass wheel, to the sur- 

 face of which a paper disk carrying four series of apertures, in 

 number 80, 60, 50, 40, is pasted. This permits the successive sounds of 

 a perfect accord to be produced by passing the luminous ray iuto the 

 apertures of a series and removing the support of the wheel itself, 

 and perfect superposed accords to be produced by leaving the sup- 

 port of the wheel immovable and concentrating, with a cylindrical 

 lens, the light upon the four series of apertures at the same time. 

 Now no rigid vibrating plate known is susceptible of producing 

 such effects. (3) Moreover the sounds produced do not change, 

 either in timbre or height, with the thickness and width of the 

 receiving plates ; they do not even sensibly change in intensity with 

 the breadth or even with the thickness, in transparent plates like 

 glass and mica, between wide limits, which for glass in particular 

 extend from 0*5 millim. to 2 or 3 centims. thickness. This per- 

 mitted me to employ receiving plates of 1 square centim., particu- 

 larly tourmaline plates of that dimension*. (4) A cracked, split 

 plate of glass, copper, aluminium, &c, produces very sensibly the 

 same effects as when it is intact. 



II. The nature of the molecules of the receiver, and their mode of 

 aggregation, do not appear to exercise a predominant part in influen- 

 cing the nature of the sounds produced. In fact, (1) with equal 

 thickness and surface, the receivers, whatever their nature may be, 

 produce sounds of the same height. (2) When the thickness of 

 the receiving plates diminishes more and more, the specific differ- 

 ences existing between their modes of producing the phenomenon 

 become more and more attenuated when their surface exposed to 

 the radiations is made identical — for instance, by covering them all 

 with a pellicle of lampblack. (3) The effect produced by ordinary 

 radiations is, cceteris paribus, very nearly the same for transparent 

 substances as different as glass, mica, Iceland spar, gypsum, quartz 

 cut parallel or perpendicular to the axis. It is the same when 

 polarized radiations are employed — for example, by means of a 

 Nicol. 



III. Radiophonic sounds certainly result from the direct action of 

 the radiations upon the receivers ; for (1) the intensity of the pheno- 

 menon is gradually diminished by diminishing the quantity of radia- 

 tions received, by aid of diaphragms of variable aperture. (2) The 

 radiations being polarized, and a thin analyzer, such as a plate of 

 tourmaline, being taken for the receiving plate, the sounds produced 



* Besides, for opaque plates, the thinner they are, the greater is the in- 

 tensity of the sounds; copper, aluminium, platinum, and especially zinc 

 foil, of J-q of a millim. for example, gives excellent results. 



