ADVERTISEMENT. 



The present memoir, describing experimeuts with ionized air, is the result of 

 a series of investigations by Pi-ofessor Bams wliich were carried on from 1893 to 

 1895, under aid from Mi-. Clarence King and Doctor Alexander Graham Bell, and 

 later continued under a grant from the Smithsonian Institution. 



This research is ti'ibutary to an investigation of the coloi-s of cloudy condensa- 

 tion. Lord Rayleigh's famous theory, if applied, would stop at the deep reds of 

 the first order terminating in opaque, whereas in the laboratory experiments, ex- 

 ceptionally brilliant colors extending almost into the third order of Newton's series 

 may be produced. 



It is thus essential as a preliminaiy step to investigate appi-opriate means for 

 the production of nuclei, to determine their number per cubic centimetre, their 

 velocity, their association with ionization, tiie effect of the presence of an electric 

 field, etc. This is the general trend of the work of the present volume though the 

 ex[)eriments have a sj)ecial interest a|)art from their ultei'ior purposes. 



The endeavor is made with the aid of the condensation tube (which pi'oves to 

 be unique in its adaptation to the present ends) to show that the nucleus has a 

 specific velocity of its own, and that this is retained even in the absence of an 

 electric field. The application of this principle to plate, to tubular, and to spherical 

 condensers leads in every case, and in spite of the variation of method, to an oi'der 

 of values as to the number of particles in action, agi'eeiug with the data obtained 

 by other investigators from different ex[)eriments and theoretically different points 

 of view. 



In accordance with the rule adopted by the Smithsonian Institution the work 

 has been submitted for examination to a Committee consistincj of Professor Wilder 

 D. Bancroft, of CcM-nell University, and Professoi' Edgar F. Smith, of the University 

 of Pennsylvania, and having been recommended foi' publication, it is herewith 

 presented in the series of Contributions to Knowledge. 



S. P. LANGLEY, 



SECRETAEY. 



Smithsonian Institution, 



Washington, June, 1901. 



