RADIOPHONY. 



787 



specification of " inability to discharge the powers and 

 duties of said office," as one of the contingencies which 

 calls the V ice-President to the exercise of presidential 

 functions ? 



Is the inability limited in its nature to long-con- 

 tinued intellectual incapacity, or has it a broader 

 import ? 



What must be its extent and duration? 



How must its existence be established ? 



Has the President, whose inability is the subject of 

 inquiry, any voice in determining whether or not it 

 exists," or is the decision of that momentous and deli- 

 cate question confided to the Vice-President, or is it 

 contemplated by the Constitution that Congress should 

 provide by law precisely what should constitute inabil- 

 ity, and how and by what tribunal or authority it should 

 be ascertained ? 



If the 'inability proves to be temporary in its nature, 

 and during its continuance the Vice-President lawfully 



exercises the functions of the Executive, by what tenure 

 does he hold his office ? 



Does he continue as President for the remainder of 

 the four years' term 3 



Or would the elected President, if his inability 

 should cease in the interval, be empowered to re- 

 sume his office ? 



And if having such lawful authority he should exer- 

 cise it, would the Vice-President be thereupon empow- 

 ered to resume his powers and duties as such? 



I can not doubt that these important questions will 

 receive your early and thoughtful consideration. 



Deeply impressed with the gravity of the responsi- 

 bilities which have so unexpectedly devolved uoon me, 

 it will be my constant purpose to co-operate with you 

 in such measures as will promote the glory of the coun- 

 try and the prosperity of its people. 



CHESTER A. ARTHUR. 



WASHINGTON, December 6, 1881. 



RADIOPHONY. The experiments of Gra- 

 ham Bell and Tainter have revealed an un- 

 expected molecular action induced by light 

 upon all kinds of substances. When a rapidly 

 alternating intermittent beam of concentrated 

 sunlight is cast upon a substance placed in a 

 receiver, disposed so as to expose equal sur- 

 faces to the action of the light, a musical sound 

 is produced which is audible through a com- 

 mon hearing-tube. The intensity of the mu- 

 sical tone varies greatly with different sub- 

 stances. The molecular vibrations which give 

 rise to the sonorous effects are due to those 

 rays only which are absorbed by the body. 

 This is proved by the experiment illustrated 

 in the diagram (Fig. 1). A beam of sunlight, 

 reflected by the heliostat (A), is brought to a 

 focus by the achromatic lens (B) so as to form 

 an image of the sun on the slit (0), the beam 

 being interrupted 500 to 600 times a second by 

 the revolving disk with radial openings (F). 

 The beam then, after traversing the achromatic 

 lens (D), is dispersed by the bisulphide-of-car- 

 bon prism (E), which forms a spectrum of 

 great intensity, showing all the principal ab- 

 sorption-lines of the solar spectrum. On ex- 

 ploring the spectrum with the receiver (G), 

 containing a narrow slit for the entrance of a 

 single ray, and holding the substance to be 

 examined, it was discovered that in the visible 

 region of the spectrum those places only in 

 which the absorption-lines of the substance 

 are found were capable of exciting the sonorous 

 phenomena, and that the maximum sound was 

 produced in the part of the spectrum where 

 the absorption-lines are thickest. Mercadier 

 had before obtained audible effects from sub- 

 stances examined in an intermittent beam of 

 electric light, and had established the fact that 

 the sonorous vibration is excited by those rays 

 alone which cast absorption-bands. Sounds 

 are given forth by many substances in the in- 

 visible regions of the spectrum. A number of 

 the substances experimented upon by Tainter 

 emitted the loudest sounds at the ultra-red end 



of the spectrum. In the ultra-violet no clearly 

 established results were obtained. 



The discovery of these unsuspected phenom- 

 ena has suggested to Bell and Tainter an im- 

 portant application of the principle established 

 in physical science. By noting the bands of 

 sound and silence in the ultra-red region, a 

 map of the invisible portion of the spectrum 

 for different substances can be constructed. 

 Such a spectrophone, as Professor Bell names 

 the instrument, is shown in Fig. 2. Lamp-black 

 is a substance which gives out clear sounds in 

 all parts of the solar spectrum, from the violet 

 to a point far out in the ultra-red. The sound 

 increases continuously, and attains its maxi- 

 mum in the ultra-red, and then decreases and 

 dies out just beyond the point of its maximum 

 intensity. Peroxide of nitrogen gas is a sub- 

 stance which produces sound in all parts of 

 the spectrum, except in the ultra-red ; the 

 maximum is in the blue, and a sound in the 

 ultra-violet region even is reported, though 

 doubtfully. The receiver of the spectrophone 

 is coated with lamp-black, and the cavity filled 

 with peroxide of nitrogen. The combination 

 gives clear and even sounds in all parts of the 

 spectrum. An intermittent beam of light is 

 passed through a substance whose absorption 

 spectrum is to be investigated. The absorp- 

 tion-bands of this substance are then indicated 

 by bands of silence. For determining the ab- 

 sorption-lines of bodies in the ultra-red region, 

 lamp-black alone is a sufficient medium. The 

 spectrophone, therefore, promises to be an in- 

 valuable adjunct to the spectroscope. 



Professor Tyndall, among others, suspected 

 that the musical sounds given out by gases 

 under the influence of the intermittent beam 

 were due to the rapid successive dilatations of 

 the gases caused by the radiant heat, and not 

 the light. His conjecture was confirmed when 

 he subjected bisulphide of carbon and sulphur- 

 ous ether successively to the action of the in- 

 termittent beam, and found that the former, 

 which is not a heat-absorbent, emitted no 



