February 9, 1906.] 



SCIENCE. 



229 



The Bulletin of the College of Charleston 

 Museum is a comparatively recent addition 

 to the list of publications whose object is to 

 popularize the work of museums and keep the 

 public informed of what is being done. The 

 December number is mainly devoted to an 

 article on whales and dolphins and gives a 

 brief account of the cetacea, notes on some 

 of the miiseum examples of this group and a 

 list of -books on whales. The number also 

 contains references to the occurrence of the 

 roseate spoonbill near Charleston. Under the 

 direction of Mr. Eea, the curator, the Charles- 

 ton Museum is being rearranged, relabeled 

 and generally ' modernized.' 



With the beginning of the present year, the 

 American Electrician has become part of the 

 Electrical World and Engineer, and the jour- 

 nal will be known as The Electrical World. 



SOCIETIES AND ACADEMIES. 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON. 



The 608th meeting was held on December 

 2, 1905. 



Mr. J. E. Burbank spoke on ' Recent Work 

 in Atmospheric Electricity,' with exhibition 

 of instruments of the Carnegie Institution. 

 The fundamental problem in atmospheric 

 electricity is the source of the earth's electric 

 field. The recent researches of Professors 

 Elster and Greitel, Ebert, Gerdien and others 

 have brought four new factors into the study, 

 namely, the rate of dissipation of the earth's 

 so-called permanent charge into the atmos- 

 phere; the ionization of the atmosphere; the 

 action of the radioactive emanations present 

 in the atmosphere, and the circulation of the 

 atmospheric electricity in the form of vertical 

 and convection currents. 



The paper was largely devoted to a descrip- 

 tion of the instruments and methods used in 

 measuring the ionization. The dispersion 

 apparatus of Elster and Geitel and Ebert's 

 aspiration apparatus or ion counter were de- 

 scribed. 



A new instrument recently devised by Dr. 

 Gerdien, of Gottingen, Germany, was then 

 shown. This is similar to ' Ebert's and con- 

 sists of an outer cylinder 30 cm. in diameter 



through which air is drawn by means of a fan 

 driven by hand. The inner electrode consists 

 of a tube 1.4 cm. in diameter and 24 cm. long 

 and is mounted on the post which carries the 

 aluminum leaves of the electroscope. The 

 loss in charge of this inner electrode is found 

 for an interval of time, usually five minutes, 

 during which air is drawn through the appa- 

 ratus. From the known dimensions and elec- 

 trostatic capacity of this cylinder condenser 

 and its loss of potential we can calculate in 

 absolute units the quantity X represented by 

 the product of the ionic charge (e) into the 

 number (n) of ions per c.c. and into mean 

 specific velocity (v) (cms./sec. volts/cm.), 

 and is known as the specific conductivity. 

 The discussion of the formula showed that 

 X^env was independent of the velocity of 

 the air current within wide limits; hence in- 

 dependent of wind, etc. The specific con- 

 ductivity is not a constant as with metals, 

 but varies with the ionic content of the air. 



Dr. Gerdien has used this instrument to 

 measure conductivity in balloon ascensions to 

 a height of 5,700 meters, and from a series of 

 such observations together with observations 

 of potential gradient has deduced values for 

 the intensity of the vertical currents. These 

 currents on the earth's surface amount to 

 about 2.4 X 10"^^ amperes per sq. cm. ; at a 

 height of 2,500 meters 0.8 X10-^^ and at 

 5,000 meters 0.3 X 10"^" amperes, per sq. cm. 



This instrument can be used in dense fogs 

 or even during rain. The author secured 

 some results on a sea voyage from Liverpool 

 to Boston showing that A for positive charges 

 was of the same magnitude as for negative 

 charges. Curves were exhibited showing the 

 values of the conductivity when passing into 

 and through a fog bank and also during a 

 light shower. The values of A in dense fog 

 are about one tenth to one twentieth the value 

 in clear air, but curves for both positive and 

 negative conductivity follow each other very 

 closely even in -very rapid changes of ioniza- 

 tion. 



Professor Ebert has reported to Dr. Bauer 

 that the eclipse observations on August 30, 

 1905, made by him at Palma, Majorca, in the 

 Mediterranean with his ion counter gave a 



