776 



SCIENCE 



[N. S. Vol. XXVIII. No. 726 



instrument on board the Galilee, making observa- 

 tions at sea from latitude 55° 41' north to 45° .07' 

 south, but was unable to measure the potential 

 gradient. The conductivities found gave as means 

 Xp = 1.60X10-* and X» = 1.433 X 10"* electro- 

 static units, somewhat greater than Gerdien found 

 on land. A description of the method of observa- 

 tion at sea was given and the difficulties men- 

 tioned. Calibrations of the electroscope in New 

 Zealand and at the Bureau of Standards in Wash- 

 ington showed its sensitiveness to be nearly con- 

 stant, but gradually increasing. 



C. T. R. Wilson's method of measuring the 

 earth-air current was described. He uses a test 

 plate maintained at zero potential while insulated 

 from the earth, and arrives at a value for the 

 current almost identical with that of Gerdien, 

 namely, 2.2 X lO"'" amperes. Mention was made 

 of Schering's work in Gottingen on the continuous 

 registration of the conductivity of the atmosphere, 

 and his apparatus described. He avoids satura- 

 tion currents by removing the charged body to a 

 sufficient distance from earthed conductors, and 

 obtained a trace showing the course of the con- 

 ductivity by means of an electrometer connected 

 with the charged body. 



Satterly at the Cavendish Laboratory, Cam- 

 bridge, Eve at Montreal and Ashman at the Uni- 

 versity of Chicago, have all made independent 

 determinations of the quantity of radio-active 

 emanation in the atmosphere in terms of the mass 

 of radium per cubic meter required to maintain in 

 equilibrium the observed amount of emanation. 

 Ashman condensed the emanation by cooling with 

 liquid air. Eve absorbed it with cocoanut charcoal 

 and Satterly used both methods. The results give 

 as the radium equivalent per cubic meter according 

 to Ashman 97 X 10"" gram. Eve 60 X lO"''' gram, 

 from results extending over a year, and with a 

 ratio of maximum to minimum of 7 to 1, and 

 Satterly, 88 X 10"^ gram for the charcoal method 

 and over 100 X lO"'^ for the liquid-air method. 



On board the Galilee practically no radio-active 

 deposit could be collected, yet the ionization was 

 as great as on land, tending to disprove the theory 

 that the ionization of the air is due to the radio- 

 active content. 



Attention was called to the need for a well- 

 equipped observatory for research along these lines 

 in this country, where the subject has been almost 

 entirely neglected. 

 Thermometric Lag in Galorimetry : Mr. W. P. 



White. 



Of late, in calorimetry by the method of mix- 



tures, several attempts have been made to avoid 

 an error due to the lag of the thermometer to 

 which considerable importance has been attached. 

 This error, however, does not exist at all, which 

 may be shown as follows: In a calorimetric run 

 by the method of mixtures, all the temperature 

 data lie upon a temperature-time curve whose 

 form determines both the cooling correction and 

 the main temperature interval. The exact in- 

 stant at which temperatures on this curve are 

 read is unimportant, so long as the temperature 

 intervals are preserved. If now, all temperatures 

 are plotted the same number of seconds wrong, 

 as they would be when the same lagging ther- 

 mometer is used throughout, no appreciable error 

 can result. The importance of lag in calorimetric 

 thermometers has, therefore, been greatly over- 

 estimated. 



K. L. Fakis, 

 Secretary 



THE ELISHA MITCHELL SCIENTIFIC SOCIETT OF THE 

 UNIVEESITT OF NOBTH CAEOLINA 



The 179th meeting of the society was held in 

 Chemistry Hall on Tuesday, October 13, 1908, 

 7 : 30 P.M. The program was as follows : 



" Results of the Microscopic Study of the Slate 

 near Chapel Hill," Mr. H. N. Eaton. 



" Chemical Energy," Professor J. E. Mills. 



" A Further Contribution on the Regenerative 

 Power of Sponges," Professor H. V. Wilson. 

 Alvin S. Wheelee, 

 Recording Secretary 



section or BIOLOGY, PITTSBURGH ACADEMY OF 

 SCIENCE AND ART 



The first meeting of the year was held at the 

 Carnegie Institute on Tuesday evening, November 

 10. At the invitation of the section about twenty- 

 five geologists attended the meeting, and it was 

 decided that there was sufficient interest mani- 

 fested to warrant the formation of a Geological 

 Section in Pittsburgh. As the Biological Section 

 had already prepared a program which embraced 

 a large number of topics of interest to geologists, 

 it was thought best to combine the two sections 

 for the present year at least. The meeting was 

 addressed by Director W. J. Holland, Dean M. E. 

 Wadsworth, Mr. R. R. Hice, Mr. F. Hewett, Mr. 

 F. Z. Schellenberg, Mr. E. Andrews, Mr. F. S. 

 Webster, Professor J. G. Ogden, Dr. A. E. Ort- 

 mann and the secretary of the section. 



Percy E. Raymond, 



Secretary 



