1835.] Observations on Visible Vibration. 126 



it will be seen that the production of the secondary tones 

 does not depend on the same causes which regulate the 

 nodal divisions of a string, but on circumstances which I 

 feel some hesitation in stating, as the real and satisfactory 

 causes for the production of the above results. Yet, I feel 

 that if I can only approach to an explanation, something 

 will be gained ; a small portion of a mystic page of Nature's 

 exquisite volume may perchance become divested of a small 

 portion of its obscurity, and, I am sure, that if the theory I 

 am about to propound be considered untenable, from the 

 following facts, I will immediately abandon it and seek new 

 facts to support another theory sufficient to explain the 

 phenomena of secondary tones, submitting, at the same 

 time, that the following results (62, 63, 64, 65), are suffici- 

 ently curious, in themselves, to merit some attention in 

 connexion with the almost universal phenomena of vibra- 

 tory action. 



62. I have before stated my belief (54) that the active 

 or positive vibration of a glass goblet is confined to its 

 interior, the exterior being in a negative or diminished 

 state of vibration. If one goblet be fixed within a larger 

 one, so that the latter shall completely contain the former, 

 and water be placed within and without the interior glass, 

 and the latter be vibrated, it will be seen that the exterior 

 undulae are considerably smaller in quantity and extent than 

 those within. Mercury may be employed with the same, 

 and even with more satisfactory results, as its great density 

 allows solids to rest, from its surface, against the exterior 

 or interior surfaces of the inner vessel, as may be required, 

 and the vibration or non-vibration of the solid bodies, such 

 as shots, pieces of iron wire, (fee, will, I think, sufficiently 

 indicate the positive or negative states of the two surfaces 

 of the glass. 



63. Having poured mercury within and water without 

 the interior glass, the fundamental note which was originally 

 (61) D within the stave, was lowered to G within the stave 

 when the mercury vibrated well ; a shot placed on the 

 mercury leaning against the interior surface of the inner 

 glass was violently agitated, (15) and a piece of iron wire 



earthenware or porcelain mug, basin, or cup, &c., be placed lightly on the hand, 

 and the edge struck, two notes will generally be heard, which seldom harmonize, 

 but have an interval of about one whole tone between them. 



