COMPOUND POLITICAL HEADS. 197 



Experiments with Gaseous Matter. On the 29th of November, 

 1880, 1 had the pleasure of showing to Professor Tyndall, in the labora- 

 tory of the Royal Institution, the experiments described in the letter 

 to Mr. Tainter from which I have quoted above ; and Professor Tyn- 

 dall 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 Rontgen * and Tyndall f 

 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, mer- 

 cury, iodine, and peroxide of nitrogen. The loudest sounds were ob- 

 tained 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. '\ 







THE DEYELOPMEXT OF POLITICAL INSTITUTIONS. 



By HERBERT SPENCER. 

 YII. COMPOUXD POLITICAL HEADS. 



IN the preceding chapter on chiefs and kings, we traced the develop- 

 ment of the first element in that triune political structure which 

 everywhere shows itself at the outset. We pass now to the develop- 

 ment of the second element the group of leading men among whom 

 the chief is, at first, merely the most conspicuous. Under what con- 

 ditions this so evolves as to subordinate the other two, what causes 



* " Annalen der Physik und Cbemie," 1881, No. 1, p. 155. 

 f " Proceedings of the Royal Society," vol. xxxi, p. 307. 



