SCIENCE. 



"3 



placed in the intermittent beam, emitted a faint, but dis- 

 tinct, musical sound. This bottle had been opened two 

 or three times during the day, its dryness being thus 

 vitiated by the mixture of a small quantity of common 

 air. A second similar bottle, in which sulphuric acid 

 had stood undisturbed for some days, was placed in the 

 beam : the dry air above the liquid proved absolutely 

 silent. 



On the evening of January the 7th, professor Dewar 

 handed me four flasks treated in the following manner. 

 Into one was poured a small quantity of strong sulphu- 

 ric acid ; into' another a small quantity of Nordhausen 

 sulphuric acid ; in a third were placed some fragments 

 of fused chloride of calcium ; while the fourth contained 

 a small quantity of phosphoric anhydride. They were 

 closed with well fitting india-rubber stoppers, and per- 

 mitted to remain undisturbed throughout the night. 

 Tested after twelve hours, each of them emitted a feeble 

 sound, the flask last mentioned being the strongest. 

 Tested again six hours later, the sound had disappeared 

 from three of the flasks, that containing the phosphoric 

 anhydride alone remaining musical. 



Breathing into a flask partially filled with sulphuric 

 acid instantly restores the sounding power, which con- 

 tinues for a considerable time. The wetting of the in- 

 terior surface of the flask with sulphuric acid always en- 

 feebles, and sometimes destroys the sound. 



A bulb, less than a cubic inch in volume, and contain- 

 ing a little water, lowered to the temperature of melting 

 ice, produces very distinct sounds. Warming the water 

 in the flame of a spirit-lamp, the sound becomes greatly 

 augmented in strength. At the boiling temperature the 

 sound emitted by this small bulb* is of extraordinary in- 

 tensity. 



These results are in accord with those obtained by me 

 nearly nineteen years ago, both in reference to air and to 

 aqueous vapor. They are in utter disaccord with those 

 obtained by other experimenters, who have ascribed a 

 high absorption to air and none to aqueous vapor. 



The action of aqueous vapor being thus revealed, the 

 necessity of thoroughly drying the flasks, when testing 

 other substances, becomes obvious. The following plan 

 has been found effective. Each flask is first heated in 

 the flame of a spirit-lamp till every visible trace of in- 

 ternal moisture has disappeared, and it is afterwards 

 raised to a temperature of about 400 C. While the flask 

 is still hot, a glass tube is introduced into it and air freed 

 from carbonic acid by caustic potash, and from aqueous 

 vapor by sulphuric acid, is urged through the flask un- 

 til it is cool. Connected with the ear-tube, and exposed 

 immediately to the intermittent beam, the attention of 

 the ear, if I may use the term, is converged upon the 

 flask. When the experiment is carefully made, dry air 

 proves as incompetent to produce sound as to absorb 

 radiant heat. 



In 1868 I determined the absorptions of a great num- 

 ber of liquids whose vapors I did not examine. My ex- 

 periments having amply proved the parallelism of liquid 

 and vaporous absorption, I held undoubtingly twelve 

 years ago that the vapor of cyanide of ethyl and of 

 acetic acid would prove powerfully absorbent. This con- 

 clusion is now easily tested. A small quantity of either 

 ot these substances, placed in a bulb a cubic inch in vol- 

 ume, warmed, and exposed to the intermittent beam, 

 emits a sound of extraordinary power. 



I also tried to extract sounds from perfumes, which I 

 had proved in 1861 to be absorbers of radiant heat. I 

 limit myself here to the vapors of patchouli and cassia, 

 the former exercising a measured absorption of 30, and 

 the latter an absorption of 109. Placed in dried flasks, 

 and slightly warmed, sounds were obtained from both 

 these substances, but the sound of cassia was much 

 louder than patchouli. 



Many years ago I had proved tetrachloride of carbon 

 to be highly diathermanous. Its sounding power is as 

 feeble as its absorbent power. 



In relation to colliery explosions, the deportment of 

 marsh-gas was of special interest. Professor Dewar 

 was good enough to furnish me with a pure sample of 

 this gas. The sounds produced by it, when exposed to 

 the intermittent beam, were very powerful. 



Chloride of methyl, a liquid which boils at the ordin- 

 ary temperature of the air, was poured into a small flask, 

 and permitted to displace the air within it. Exposed to 

 the intermittent beam, its sound was similar in power to 

 that of marsh-gas. 



The specific gravity of marsh gas being about half that 

 of air, it might be expected that the flask containing it, 

 when left open and erect, would soon get rid of its con- 

 tents. This, however, is not the case. After a consider- 

 able interval, the film of this gas clinging to the interior 

 surface of the flask was able to produce sounds of great 

 power. 



A small quantity of liquid bromine being poured into 

 a well-dried flask, the brown vapor rapidly diffused itself 

 in the air above the liquid. Placed in the intermittent 

 beam, a somewhat forcible sound was produced. This 

 might seem to militate against my former experiments, 

 which assigned a very low absorptive power to bromine 

 vapor. But my former experiments on this vapor were 

 conducted with obscure heat; whereas, in the present 

 instance, I had to deal with the radiation from incandes- 

 cent lime, whose heat is, in part, luminous. Now, the 

 color of the bromine vapor proves it to be an energetic 

 absorber of the luminous rays ; and to them, when sud- 

 denly converted into thermometric heat in the body of 

 the vapor, I thought the sounds might be due. 



Between the flash containing the bromine and the ro- 

 tating disc I therefore placed an empty glass cell : the 

 sounds continued. I then filled the cell with transparent 

 bisulphide .of carbon: the sounds still continued. For 

 the transparent bisulphide I then substituted the same 

 liquid saturated with dissolved iodine. This solution 

 cut off the light, while allowing the rays of heat free 

 transmission : the sounds were immediately stilled. 



Iodine vaporised by heat in a small flask yielded a 

 forcible sound, which was not sensibly affected by the 

 interposition of transparent bisulphide of carbon, but 

 which was completely quelled by the iodine solution. 

 It might indeed have been foreseen that the rays trans- 

 mitted by the iodine as a liquid would also be trans- 

 mitted by its vapor, and thus fail to be converted into 

 sound.* 



To complete the argument: — While the flask contain- 

 ing the bromine vapor was sounding in the intermittent 

 beam, a strong solution of alum was interposed between 

 it and the rotating disc. There was no sensible abate- 

 ment of the sounds with either bromine or iodine 

 vapor. 



In these experiments the rays from thelimedight were 

 converged to a point a little beyond the rotating disc. In 

 the next experiment they were rendered parallel by the 

 mirror, and afterwards rendered convergent by a lens of 

 ice. At the focus of the ice lens the sounds were ex- 

 tracted from both bromine and iodine vapor. Sounds 

 were also produced after the beam had been sent through 

 the alum solution and the ice lens conjointly. 



With a very rude arrangement I have been able to 

 hear the sounds of the more active vapors at a distance 

 of 100 feet from the source of rays. 



Several vapors other than those mentioned in this 

 abstract have been examined, and sounds obtained from 

 all of them. The vapors of all compound liquids will, 

 I doubt not, be found sonorous in the intermittent beam. 

 And, as I question whether there is an absolutely dia- 

 thermanous substance in nature, I think it probable that 



* In such bulbs even bisulphide of carbon vapor may be so nursed as 

 to produce sounds of considerable strength. 



* I intentionally use this phraseology. 



