SCIENCE 



Friday, June 11, 1909 



CO'NTESTS 



The Ions of the Atmosphere: Pbofessoe J. A. 

 Pollock 919 



The Elizabeth Thompson Science Fund 928 



The Retirement of President Eliot 928 



The Winnipeg Meeting of the British Asso- 

 ciation 929 



Sdentifie Notes and News 929 



University and Educational News 932 



Discussion and Correspondence: — 



On the Teaching of the Elements of Embry- 

 ology: Pbofessoe Fbank R. Lillie. Gen- 

 era icithout Species : Db. J. A. Allen. The 

 Origin of the Moon : Pbofessob Andbew H. 

 Patteeson 932 



Scientific Books: — 



Gibson on Sdentifie Ideas of To-day: Pbo- 

 fessoe W. S. Feanklin. Normentafel zur 

 Entmchlungsgeschichte des Menschen: Pbo- 

 fessoe Feedebic T. Lewis 937 



Special Articles: — 



Notice of Two New Horizons for Marine 

 Fossils in Western Pennsylvania : Peect E. 

 Eatmoito. New Facts about Bacteria of 

 California Soils: Chas. B. Lipman. A 

 Scheme to Represent Type Heredity in 

 Man: Robebt Bennett Bean. A New 

 Edible Species of Amanita: Pbofessoe 

 Geoege F. Atkinson 940 



The American Association of Museums: De. 

 Paul M. Rea 944 



Societies and Academies: — 



The Geological Society of Washington: 

 Fbancois E. Matthes, Philip S. Smith. 

 The Philosophical Society of Washington: 

 R. L. Fabis. The New York Section of the 

 American Chemical Society: C. M. Joyce. . 945 



MSS. intended fer publication and books, etc., intended for 

 rcTiew should be sent to the Editor of Science, Garrison-on- 

 Hudson, N. Y. 



THE IONS OF THE ATMOSPHERE^ 

 As one of the results of the recent de- 

 velopment of electrical science it is consid- 

 ered that throughout the air in its normal 

 state, and in other gases in a similar con- 

 dition, there exists a small number of mole- 

 cules, or groups of molecules, which are 

 distinguished from the vast host of their 

 fellows in being electrified. Each of these 

 electrified entities, whatever its structure, 

 is called an ion, and of ions there are two 

 main classes, the one containing those 

 which are positively, the other those which 

 are negatively, electrified. The notion of 

 the ion, in this connection, arises from at- 

 tempts to reach a simple description of 

 the facts associated with the conduction of 

 electricity through gases, and the hj^oth- 

 esis admirably fulfils its purpose. 



The number of ions in the air can be 

 greatly increased by exposing it to the in- 

 fluence of Eontgen rays, or to the radia- 

 tions from radium or other radio-active 

 bodies, and it is from investigations con- 

 nected with this artificially produced 

 ionization that most of our present knowl- 

 edge of ions is derived. For the most 

 interesting account of these researches I 

 refer you to the address delivered before 

 this section at Dunedin in 1904 by the 

 present distinguished president of the asso- 

 ciation. For my immediate purpose I 

 have to remind you of one result: in an 

 electric field, in addition to the motion of 

 molecular agitation shared by all the con- 

 stituents of a gas, the ions, in virtue of 

 their charge, acquire a velocity whose aver- 

 age value depends on the electric intensity 



' Presidential address before Section A of the 

 Australasian Association for the Advancement of 

 Science. 



