562 



SCIENCE 



[N. S. Vol. XXVII. No. 693 



Members of the Sectional Committee — D. C. 

 Miller, K. E. Guthe, A. D. Cole, F. E. Nipher, 

 E. L. Nichols, A. Trowbridge, E. B. Rosa, A. P. 

 Carman. 



In the afternoon of December 31, the 

 retiring vice-president, Professor Wallace 

 C. Sabine, delivered a very interesting ad- 

 dress on "The Origin of the Musical 

 Scale. ' ' This was followed by an instruct- 

 ive and entertaining account of "Physical 

 Research at a Mountain Observatory," by 

 Professor Geo. E. Hale, of Mt. Wilson, 

 California. Joint meetings of the two 

 societies were held on Monday, Tuesday, 

 Wednesday and Thursday. The attend- 

 ance was uniformly large and fully 

 one hundred and fifty were present 

 to hear the vice-presidential address. 

 Fifty-two papers were presented covering 

 a wide variety of topics, and many of 

 them of very great interest. There was 

 a hotel headquarters for physicists, a 

 feature which added much to the pleasure 

 and profit of the meeting. 



The abstracts and titles of the papers 

 presented at the joint-sessions of the two 

 societies are given below. 



The Discharge of Electricity from Pointed 

 Conductors: John Zelent, University 

 of Minnesota. 



The way in which the discharge of elec- 

 tricity from steel sewing needles and from 

 12° cones, depends upon the sharpness or 

 diameter of the points, has been studied. 

 The potential required to start the positive 

 discharge from these points can in each 

 case be represented by a formula involv- 

 ing the diameter of the point. The rela- 

 tion between the potential of a point and 

 the current flowing from it can be repre- 

 sented in each case by a formula involving 

 the diameter of the point and the potential 

 required to start a current. During the 

 positive discharge from steel points masses 

 of iron oxide form on the tips of the 



points. This also occurs to a much smaller 

 extent during the negative discharge. The 

 current, flowing to a spherical surface from 

 a point placed at its center of curvature, 

 distributes itself quite uniformly over the 

 whole surface of the hemisphere opposite. 

 With diminution of pressure the discharge 

 between a point and a plane takes place 

 at gradually lower and lower potentials, 

 and the current increases more and more 

 rapidly with change of voltage. Below a 

 pressure of one centimeter the potential 

 required for the discharge drops rapidly to 

 about 400 volts as the pressure is reduced 

 to a few hundredths of a centimeter, and 

 then at about a hundredth of a centimeter 

 it begins to increase again rapidly. 



Notes on Spark Potentials: R. F. Eakhart, 



Ohio State University. 



Point and Plane. — Measurements were 

 made on the P.D. required to cause a dis- 

 charge between a needle point and a plane 

 surface, for very small distances. 



Potentials were secured from a bank of 

 storage cells. Distances were measured by 

 means of an interferometer. 



Curves are shown representing the rela- 

 tion between distance and potential. One 

 family of curves represents discharge from 

 a positive point for pressures of 75 em., 37 

 cm. and 25 cm. In a similar manner re- 

 sults obtained for point negative are shown. 



The least potential required for ioniza- 

 tion of air under these conditions is 338 

 volts, a value somewhat less than has been 

 previously determined for plane electrodes. 



Potentials less than 338 volts can pro- 

 duce a discharge, but of a different char- 

 acter. Such discharge is probably pro- 

 duced by the projection of corpuscles or 

 metal atoms. The polarity of the point 

 does not influence the discharge for the 

 abnormally small distances. For greater 

 distances discharge occurs more readily 

 from a negative than for a positive point. 



