42 THE POPULAR SCIENCE MONTHLY. 



A small quantity of liquid bromine being poured into a well-dried 

 flask, the brown vapor rapidly difused 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 experi- 

 ments, which assigned a very low absorptive power to bromine vapor. 

 But my former experiments on this vapor were conducted with ob- 

 scure heat ; whereas, in the present instance, I had to deal with the 

 radiation from incandescent lime, whose heat is, in part, luminous. 

 Now, the color of the bromine vapor proves it to be an energetic ab- 

 sorber of the luminous rays ; and to them, when suddenly converted 

 into thermometric heat in the body of the vapor, I thought the sounds 

 mi2:ht be due. 



Between the flasks containing the bromine and the rotating disk, I 

 therefore placed an empty glass cell : the sounds continued. I then 

 filled the cell with transparant 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, vaporized by heat in a small flask, yielded a forcible sound, 

 which was not sensibly affected by the interposition of transparant 

 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 transmitted by its 

 vaj^or, and thus fail to be converted into sound.* 



To complete the argument : While the flask containing the bro.- 

 mine vapor was sounding in the intermittent beam, a strong solution 

 of alum was interposed between it and the rotating disk. There was 

 no sensible abatement of the sounds with either bromine or iodine 

 vapor. 



In these experiments the rays from the lime-light were converged 

 to a point a little beyond the rotating disk. In the next experiment 

 they were rendered parallel by the mirror, and afterward rendered 

 convergent by a lens of ice. At the focus of the ice-lens the sounds 

 were extracted 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. 



^Vith a very rude arrangement I have been able to hear the sounds 

 of the more active vapors at a distance of one hundred 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 liquors will, I doubt not, be found sonorous in the 

 intermittent beam. And, as I question whether there is an absolutely 



* I intentionally use this phraseology. 



