Experiments with Gaseous Matter.—On the 29th of November, 1880, 1 had the pleasure of showing to Professor Tyndall, in the laboratory of the Royal Institution, the experiments described in the letter to Mr. Tainter from which I have quoted above; and Professor Tyndall at once expressed the opinion that the sounds were due to rapid changes of temperature in the body submitted to the action of the beam. Finding that no experiments had been made at that time to test the sonorous properties of different gases, he suggested filling one test-tube with the vapor of sulphuric ether (a good absorbent of heat), and another with the vapor of bisulphide of carbon (a poor absorbent), and he predicted that if any sound were heard it would be louder in the former case than in the latter.
The experiment was immediately made, and the result verified the prediction.
Since the publication of the memoirs of Röntgen and Tyndall we have repeated these experiments, and have extended the inquiry to a number of other gaseous bodies, obtaining in every case similar results to those noted in the memoirs referred to.
The vapors of the following substances were found to be highly sonorous in the intermittent beam: Water-vapor, coal-gas, sulphuric ether, alcohol, ammonia, amylene, ethyl bromide, diethylamene, mercury, iodine, and peroxide of nitrogen. The loudest sounds were obtained from iodine and peroxide of nitrogen.
I have now shown that sounds are produced by the direct action of intermittent sunlight from substances in every physical condition (solid, liquid, and gaseous), and the probability is, therefore, very greatly increased that sonorousness under such circumstances will be found to be a universal property of matter.
[To te continued.]
By HERBERT SPENCER.
VII.—COMPOUND POLITICAL HEADS.
IN the preceding chapter on chiefs and kings, we traced the development of the first element in that triune political structure which everywhere shows itself at the outset. We pass now to the development of the second element—the group of leading men among whom the chief is, at first, merely the most conspicuous. Under what conditions this so evolves as to subordinate the other two, what causes
- "Annalen der Physik und Cbemie," 1881, No. 1, p. 155.
- "Proceedings of the Royal Society," vol. xxxi, p. 307.