6 THE ABSORPTION SPECTRA OF SOLUTIONS. 



studied the velocity of the light streamers, and in some instances have found 

 indications that the emitting centers carried a negative charge. The subject is 

 such a complicated one, however, that it must be stated that our knowledge at 

 present concerning the constitution of these emission centers is extremely 



meager. 



THE EMISSION CENTERS OF FLAMES AND ARCS. 



The study of the Zeeman effect has shown beyond a doubt that the vibra- 

 tions of the emitting centers of many arc, spark, and flame lines are affected 

 by an outside magnetic field, in the same way as negative electrons would be 

 affected; and it is remarkable how closely the value of e/m, as calculated from 

 the Zeeman effect, agrees with the value as found for the cathode and jS-ray 

 particles. The Zeeman effect does not, however, give us much knowledge of 

 the radiating centers, since the electrons form only a small part of these centers. 



A very important series of experiments has been carried out by Lenard 1 

 and others. The main conclusion from this work was that the carriers of the 

 first subordinate series in the Kayser and Runge classification of spectrum 

 lines are positively charged ions. The reason that ions in liquids do not radi- 

 ate, Lenard explains as due to their being loaded down by neutral molecules. 

 The work of other investigators has made this conclusion very doubtful, so 

 that, as in the case of spark and canal-ray spectra, it must be concluded that 

 at present nothing is known with certainty as to what the constitution of the 

 radiating centers may be. 



Schumann Waves. 



In 1893 Schumann studied the extremely short ultra-violet wave-lengths 

 to about X 1200. Lyman 2 , by using a concave grating, has studied the spectra of 

 hydrogen from X 2000 to X 1030, there being no radiations apparently between 

 X 3000 and X 1700. Argon possesses a rich emission spectrum in this region. 

 The spectra of carbon monoxide and dioxide seem to be very much alike, and 

 produce radiations to X 1300. Oxygen and nitrogen do not seem to emit in 

 this region. Fluorite is the only substance transparent to X 1225. Quartz 

 0.5 mm. thick absorbs everything beyond X 1500. Argon, helium, hydrogen, 

 and nitrogen in a layer of 1 cm. are perfectly transparent. The absorption of 

 air is due to the presence of oxygen. Oxygen of 9 mm. depth and 380 mm. 

 of mercury pressure has an absorption band extending from X 1750 to X 1275. 



THE POSSIBLE CATALYTIC ACTION OF LIGHT. 



Weigert 3 has worked upon the equilibrium of the gas COCl 2 and its 

 products, CO+Cb. The reaction 



C0 + C1 2 -C0C1 2 



is accelerated by the action of light, but the position of the final equilibrium is 

 unaffected by the action of the light, and is a function only of the temperature. 

 The light thus acts as a catalyzer and not as a source of energy. 



'Ann. d. Phys., 9, 642 (1902); 11, 6-19 (1903); 12, 475 (1903); 12, 737 (1903); 17, 

 197 (1905). 



2 Ibid., 77, 777 (1907). 



3 Le Radium, 4, 373 (1907): Ann. .1. Phys., 24, 24:; (1907). 



