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Mechanical operation of sound-waves
Nov, 1879.]
Mechanical Operation of Sound-wave.s.
353
N u m b e r o f O s c i l l a t i o n s i n a M u s i c a l l~ote.--Pfaundler coneluded, fi,om obserwttions with a siren, that two oseillations were sufficient to produce "~ note. Felix Auerbaeh, from a combination of physiological, psychologieal, physical and musi(~d considerations, finds that probably about twenty oscillations arc necessary. His views are confirmed by previous observations of Exner, Von Kries and Toepler.-Anat. der Phys. ~ml (?t,~m. C. L a r g e M a p o f t h e Solar S p e c t r u m . - - M . Thollon h;~,~exhibited to the French h(~tdemy a map of the visible portion of the solar sp(~trum, carefully executed in It'd),, with the help of his large spectn~seope. It is 10 metres (32"809 ft.) long, extending from A to It, and exhibiting about 4000 lines. Angstrbm's map contained 1600 lines, and was 3 metres long. Ite calls special attention to the singular resemblance between the groups A and B, which never betbre have been so completely resolved, and proposes the following claasifi(ation of lines : 1. Lines tbrmed by a nebulosity without nucleus. 2. Lines consisting of a nucleus without apparent nebulosity. 3. Lines having both nucleus and nebulosity, the lattel, predominating. 4. Lines having nucleus and nebuloslty, the tbrmer predominating. H e gives a description of his apparatns~ and states that the only precaution necessary in using it is to guard the prisms e~refully from any variation of temperature.--(?omptes Renders. C. M e c h a n i c a l O p e r a t i o n o f S o u n d - W a v e s . ~ K . H. Schcllbach ,(nd E. E. Boehn have experimented with waves of sound, in illustration of the wave theory of light. Connecting two Leyden jars with the conductors of a Itoltz electrical machine, so 'as to produce sparks of I ecntimetre ('39 in.) between the. balls of the discharger, concentric rings were tbrmed in coal-dust sprinkled on a gla.~s plate 4 (~ntlmetm~ (1"57 in.) fl'om the balls. The longcr the spark the more strongly marked were the rings. By reflecting the rep(~rts of the discharges, by means of parallel walls and mirrors of various kinds, the dustwaves were made to assume such forms as are theoretically dedueible from the reflection and refraction of light, thus visibly confirming the views of IIuyghens and Yomlg. ~£hat the results are not modified in any way by mere electrical action can be readily shown by substituting explosive gas or powder tbr the sp'trks. From ten to twenty sparks or explosions were generally sufficient to show tile character of the waves and of their nodal intersections.- -Ann. d. Phys. und Chem. C. 25 WJ~Ol;~ No. VoL CVII I.---(THtru~ 8E~u~% Vol. Ix x viii.)
Mechanical Operation of Sound-wave.s.
353
N u m b e r o f O s c i l l a t i o n s i n a M u s i c a l l~ote.--Pfaundler coneluded, fi,om obserwttions with a siren, that two oseillations were sufficient to produce "~ note. Felix Auerbaeh, from a combination of physiological, psychologieal, physical and musi(~d considerations, finds that probably about twenty oscillations arc necessary. His views are confirmed by previous observations of Exner, Von Kries and Toepler.-Anat. der Phys. ~ml (?t,~m. C. L a r g e M a p o f t h e Solar S p e c t r u m . - - M . Thollon h;~,~exhibited to the French h(~tdemy a map of the visible portion of the solar sp(~trum, carefully executed in It'd),, with the help of his large spectn~seope. It is 10 metres (32"809 ft.) long, extending from A to It, and exhibiting about 4000 lines. Angstrbm's map contained 1600 lines, and was 3 metres long. Ite calls special attention to the singular resemblance between the groups A and B, which never betbre have been so completely resolved, and proposes the following claasifi(ation of lines : 1. Lines tbrmed by a nebulosity without nucleus. 2. Lines consisting of a nucleus without apparent nebulosity. 3. Lines having both nucleus and nebulosity, the lattel, predominating. 4. Lines having nucleus and nebuloslty, the tbrmer predominating. H e gives a description of his apparatns~ and states that the only precaution necessary in using it is to guard the prisms e~refully from any variation of temperature.--(?omptes Renders. C. M e c h a n i c a l O p e r a t i o n o f S o u n d - W a v e s . ~ K . H. Schcllbach ,(nd E. E. Boehn have experimented with waves of sound, in illustration of the wave theory of light. Connecting two Leyden jars with the conductors of a Itoltz electrical machine, so 'as to produce sparks of I ecntimetre ('39 in.) between the. balls of the discharger, concentric rings were tbrmed in coal-dust sprinkled on a gla.~s plate 4 (~ntlmetm~ (1"57 in.) fl'om the balls. The longcr the spark the more strongly marked were the rings. By reflecting the rep(~rts of the discharges, by means of parallel walls and mirrors of various kinds, the dustwaves were made to assume such forms as are theoretically dedueible from the reflection and refraction of light, thus visibly confirming the views of IIuyghens and Yomlg. ~£hat the results are not modified in any way by mere electrical action can be readily shown by substituting explosive gas or powder tbr the sp'trks. From ten to twenty sparks or explosions were generally sufficient to show tile character of the waves and of their nodal intersections.- -Ann. d. Phys. und Chem. C. 25 WJ~Ol;~ No. VoL CVII I.---(THtru~ 8E~u~% Vol. Ix x viii.)