A small quantity of liquid bromine being poured into a well-dried flask, the brown vapor rapidlyitself 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 incandescent 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 suddenly converted into thermometric heat in the body of the vapor, I thought the sounds might 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 withbisulphide 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 bisulphide of carbon, but which was completely quelled by the iodine solution. It might indeed have been foreseen that the rays transmitted by the iodine as a liquid would also be transmitted by its vapor, and thus fail to be converted into sound.
To complete the argument: While the flask containing the bromine 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.
With 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.