394 



SCIENCE 



[N. S. Vol. XLIII. No. 1107 



with key, Fig. 3, are submitted. Compara- 

 tively weak magnetic fields were employed.^ 

 The two coincident deflecting fields are 

 sketched in Fig. 3, in which the direction of 



L„\.. 



-ions 







Fig. 3. 



ttie electrostatic field is indicated by the minus 

 and plus signs, while the arrow heads show 

 the direction of the magnetic field. Again, 

 magnetic deflections are up or down, while 

 electrostatic deflections are to the right or left. 

 The undeflected spot is due to carriers that 

 have lost their charge before entering the de- 

 flecting fields. In these photographs. Figs. 1 

 and 2, the traces due to the positive and nega- 



2 For arrangement of apparatus see C. T. Knipp, 

 Phys. Bev., Vol. XXXIV., March, 1912. 



tive ions unite at the central undeflected spot, 

 the portion to the right of being due to 

 positive ions and that to the left negative ions, 

 while the trace e, due to electrons, is distinctly 

 separated from and at some distance from 

 it, and as we should expect, is in the same 

 quadrant as the heavier negative ions. In 

 Fig. 1 the time of exposure was 10 min- 

 utes, electrostatic field 2,070 volts per centi- 

 meter, magnetic field 1.7 amperes, and the 

 vacuum .011 mm. mercury; while in Fig. 2 

 the corresponding values were 20 min., 2,070 

 volts, 2.25 amperes, and .005 mm. mercury. 

 The effect of the stronger magnetic field is 

 distinctly shown in Fig. 2 by the increased dis- 

 placement from of the trace due to the elec- 

 trons. 



Chas. T. Knipp 

 Laboratory of Physics, 

 University op Illinois 



THE AMERICAN ASSOCIATION FOR 

 THE ADVANCEMENT OF SCIENCE 



SECTION E— GEOLOGY AND GEOGRAPHY 



The sixty-eighth meeting of Section E, Geology 

 and Geography, of the American Association for 

 the Advancement of Science, was held in Orton 

 Hall, Ohio State University, Columbus, Ohio, De- 

 cember 28 and 29, 1915. Vice-president C. S. 

 Prosser presided. Professor B. D. Salisbury, Uni- 

 versity of Chicago, was elected vice-president of 

 the association, and chairman of Section E for 

 the next meeting, to be held in New York. Dr. 

 C. P. Berkey, Columbia University, was elected a 

 member of the council. Dr. J. W. Beede, Univer- 

 sity of Indiana, a member of the sectional com- 

 mittee, and Dr. E. B. Cumings, University of 

 Indiana, a member of the general committee. 



The titles and abstracts of papers presented be- 

 fore Section E are given below: 



The Classification of the Niagaran Formations of 

 Western Ohio: Charles S. Prosser. 

 A series of sections along Ludlow Creek, near 

 Covington and near Lewisburg in western Ohio, 

 which extend from the upper part of the Eichmond 

 formation to near the top of the Niagaran series 

 are fully described. Also the Derbyshire Falls 

 section, near Laurel, Indiana, is described and it 

 is shown that this important and well-known lime- 

 stone extends into Ohio and is worked at several 



