Makch 17, 1916] 



SCIENCE 



393 



concentrations) of the ions of the acid. These 

 activities are shown to decrease with increas- 

 ing concentration much more rapidly than do 

 the ion-concentrations derived in the usual 

 way from the electrical conductance ratio. 

 Y. Effects of Centrifugal Force on the Polarity 



of the Eggs of Crepidula: Edwin G. Conk- 



LiN, Department of Biology, Princeton 



University. 



It is diiBcult, but not absolutely impossible, 

 to change the polarity of eggs and cleavage 

 cells, and the persistence of polarity and the 

 restoration of dislocated parts to normal con- 

 dition is connected with a somewhat resistant 

 framework of protoplasmic strands. 



8. The Emission Quanta of Characteristic 

 X-Rays : David L. Webster, Jefferson Phys- 

 ical Laboratory, Harvard University. 



To excite any characteristic radiation it is 

 necessary to use a potential above a critical 

 value. The lines all increase in the same 

 ratio for any given increase of potential. 

 There is reason to believe that the character- 

 istic rays are always a result of excitation of 

 higher frequency oscillators. 



9. The Results of Investigations of the Ecol- 

 ogy of the Floridian and Bahaman Shoal- 

 Water Corals: Thomas "Wayland Vaughan, 

 U. S. Geological Survey, Washington, D. C. 

 The ability of corals to remove sediment 



from their surfaces, their mechanism for 

 catching food, their carnivorous nature, their 

 relation to light and temperature, and so on, 

 have been studied. 



10. Cambrian Trilohites: Charles D. Wal- 

 COTT, Smithsonian Institution, Washington, 

 D. 0. 



Data have been assembled to aid in clearing 

 up some of the problems of formations of the 

 Appalachian region by a careful comparison 

 of portions of their contained faunas with 

 those of other localities. 



11. The Minute Structure of the Solar Atmos- 

 phere: George E. Hale and Ferdinand 

 Ellerman, Mt. Wilson Solar Observatory, 

 Carnegie Institution of Washington. 



The minute structure of the quiescent solar 

 atmosphere resembles that of the photosphere. 

 The results apparently support the hypothesis 



that the solar atmosphere consists of parallel 

 columns of ascending and expanding gases, 

 but such questions as the dimensions of the 

 columns and the direction of motion and veloc- 

 ity are reserved for subsequent discussion. 

 12. Monochromatic Photography of Jupiter 



and Saturn: E. W. Wood, Department of 



Physics, Johns Hopkins University. 



The variation of the appearance of Saturn 

 and Jupiter when photographed with light 

 of different wave-lengths suggests a mist or 

 dust in the planet's atmosphere which scatters 

 the shorter wave-lengths. 



Edwin Bidwell Wilson 



Massachusetts Institute of Technology 



SPECIAL ARTICLES 



PHOTOGRAPHS SHOWING THE RELATIVE DE- 

 FLECTION OF THE POSITIVE AND OF 

 THE NEGATIVE IONS AS COMPARED 

 WITH THAT OF THE ELECTRON 



Positively and negatively charged ions, 

 atomic in size (commonly called " retrograde 

 rays"), accompany the stream of electrons 

 issuing from the cathode in a highly exhausted 

 discharge tube. Thomson^ studied their prop- 

 erties by placing a photographic plate within 

 the tube in such a position as to receive these 

 rays after being deflected simultaneously by 

 an electric and a magnetic field. When the 

 fields are coincident (not crossed) the dis- 

 placements on the photographic plate are in 

 directions at right angles to each other. The 

 photographic method is now in common use. 



To the writer's knowledge no photographs, 

 however, have been published in which all three 

 of the component carriers — the positive ion, 

 the negative ion and the electron — are shown 

 simultaneously on the same plate. Since the 

 mass of the electron is only 1/1700 that of the 

 hydrogen atom, and since the square of the 

 magnetic deflection varies inversely as the 

 mass, it follows that the electron is driven off 

 the plate by a magnetic fleld that would give 

 the ion only an appreciably small deflection. 

 By weakening the magnetic field the trace due 

 to the electrons may be retained on the plate. 



Two full-sized photographs, Eigs. 1 and 2, 



1 J. J. Thomson, "Rays of Positive Electricity," 

 pp. 75, 1913. 



