OCTOBEE 19, 1900.] 



SCIENCE. 



613 



method which ought to have been generally 

 adopted, of arranging the instruments with each 

 kind by the different makers in one case, in- 

 stead of a complete line by each maker in a 

 case by itself. An ingenious modification of 

 Foucault's pendulum was seen at the Paris Ob- 

 servatory. It was only one meter long, but it 

 showed the fact of the rotation of the earth 

 after the lapse of fifteen seconds. 



Professor Hallock described a peculiar light- 

 ning discharge he had observed at Lake Cham- 

 plain. The flash came unexpectedly from a 

 cloud about two miles from where the main 

 shower was falling. It struck on a mass of 

 rock, and on examining this it was found that 

 instead of there being one or a few places where 

 the lightning had struck, it was covered with 

 innumerable little spots, each one indicating 

 where a part of the flash had struck. 



William S. Day, 



Secretary. 



NOTES ON PSYSIC8. 



THE GALTON WHISTLE. 



In the Annalen der Physik for July, 1900, 

 Edelmann describes an improved form of the 

 Galton whistle for use in studying the limits of 

 audibility of high pitch sounds. This improved 

 form of whistle is similar to the locomotive 

 whistle in design, the vibrating air column be- 

 ing from 2 to 4 millimeters in diameter and 

 from 0.7 to 5 or more millimeters in length. 

 With a whistle 2 mm. in diameter Edelmann 

 has produced sound waves, using the word 

 sound in its physical sense, of 2 mm. wave- 

 length, corresponding to a vibration frequency 

 of 170,000 double vibrations per second. This 

 is nearly an octave higher than the highest 

 pitch obtained by Konig in 1899. 



Edelmann determined the pitch by measuring 

 the wave-length of the sound as indicated by 

 Kundt's dust figures, in an elongated glass 

 tube resonator. This resonator for the very 

 high pitch waves was less than a millimeter in 

 diameter of bore and about ten millimeters in 

 length. 



The present writer remembers well a very 

 striking lecture experiment by Professor Kundt 

 in 1890, in which the pitch limit of audibility 

 was demonstrated by a Galton whistle, the 



actual existence of the physical sound, when 

 the whistle was adjusted to give more than 

 about 40,000 vibrations per second, was beauti- 

 fully shown to a large audience by the effect of 

 the whistle upon a sensitive gas flame. 



THE GENESIS OP THE IONS IN THE DISCHARGE 

 OF BLECTEICITY THROUGH GASES. 



The phenomena of the electric discharge 

 through gases seemed only a few years ago to 

 be so complicated that physicists almost de- 

 spaired of finding an hypothesis which might 

 bring order out of the mass of experimental re- 

 sults which had accumulated. 



The discovery of the Rontgen rays stimu- 

 lated research in this field greatly, and the ob- 

 servation that these rays in passing through a 

 gas cause it to become an electrical conductor 

 soon gave fixedness to the idea that a gas con- . 

 ducts electricity by having its molecules broken 

 up into positively and negatively charged parts 

 or ions which wander about through the gas. 



This ionic hypothesis has already been of 

 great value in suggesting lines of research ; and 

 the rapidly accumulating results of these recent 

 researches, interpreted, of course, through the 

 ionic hypothesis itself, show, under the widest 

 variety of conditions, a degree of consistency 

 which is i-apidly giving to the ionic hypothesis 

 the dignity of an established theory. 



Some of the most striking applications of the 

 ionic hypothesis have been noted in Science 

 during the past three years. 



Pkofessor J. J. Thomson, in the Philosophical 

 Magazine for September, points out in a paper 

 entitled ' The genesis of the ions in the dis- 

 charge of electricity, through gases,' why the 

 dielectric strength of a gas is approximately 

 proportional to the pressure of the gas ; why 

 the dielectric strength of a thin layer of gas is 

 greater than the dielectric strength (volts per 

 centimeter) of a thick layer of the same gas ; 

 and he explains the striations of the positive 

 column or glow in a Geissler tube. 



The reader should keep in mind that the sci- 

 entific explanation of a thing is a description of 

 the thing in the simplest possible terms. Many 

 scientists feel an objection to the use of the word 

 explanation in that its use tends to confirm a 

 hearer in the acceptance of the figments of his 



