80 Intelligence and Miscellaneous Articles. 



present the variations of intensity corresponding to those of the 

 radiation itself when the polarizer or analyzer is rotated, 



IV. The phenomenon seems to result chiefly from an action upon the 

 surface of the receiver; for its intensity greatly depends upon the 

 nature of the surface. Every operation that diminishes the reflect- 

 iug-power and augments the absorptivity of the surface influences 

 the phenomenon ; roughened, tarnished, oxidated surfaces are the 

 most suitable. 



The intensity of the phenomenon is considerably augmented 

 when the surface is coated with certain black substances, in powder 

 or not, such as bitumen of Judea, platinum-black, and especially 

 lampblack ; but this effect is not particularly sensible unless the 

 coated plates are very thin : thus, if the thickness be from about 

 -j^ to T 2 D of a millimetre, remarkable effects are obtained. I have 

 consequently constructed very sensitive radiophonic receivers with 

 the aid of very thin plates of zinc, glass, mica, smoked. The em- 

 ployment of these sensitive receivers has permitted me to arrive at 

 the following result : — 



Y. Radiophonic effects are relatively very intense. In fact, I can 

 actually obtain them not only with the radiations of the sun and of 

 an electric lamp, but with the oxyhydrogen-light, the flame of an 

 ordinary gas-burner, and consequently with the radiations from 

 intermediate sources, such as petroleum-lamps, a platinum spiral 

 heated to redness by a Bunsen burner, &c. 



VI. Radiophonic effects appear to be produced chiefly by the radia- 

 tions of great wave-length, called calorific. In order to demonstrate 

 this, without stopping for the moment at the employment of cells 

 filled with absorbent liquids such as alum, iodine dissolved in sul- 

 phide of carbon, &c, the effect of which cannot be very pure, I 

 tried to explore with a sensitive receiver the spread-out spectrum 

 of the acting radiations. I succeeded in doing so with the electric 

 light of 50 Bunsen elements and by employing ordinary lenses and 

 a prism of glass. I ascertained that the maximum effect is pro- 

 duced by the red and invisible infra-red radiations ; starting from 

 the yellow and proceeding to the violet and beyond, under the con- 

 ditions under which I worked I did not obtain any sensible effect. 

 The experiment has at different times been realized with recei- 

 vers of smoked glass, platinum-blacked platinum, and zinc with its 

 surface bare. 



I think I ought to signalize the preceding facts, which have ap- 

 peared to me certain. Many points still remain forme to signalize 

 and elucidate ; this shall be the aim of an early subsequent commu- 

 nication. — Comptes Rendus de VAcademie des (Sciences, Dec. 6, 1880, 

 t. xci. pp. 929-931. 



