124 Mr. Tomlinsons Experiments and [Aug. 



Article VI. 



Expei'iments and Observations on Visible Vibration. By 



Charles Tomlinson, Esq. 



(continued from vol. i.'p. 439. J 



60. It is known that during the vibration of a stretched 

 cord, a series of tones may be heard, together with the 

 fundamental note, which are called harmonics, from the 

 circumstance of their forming harmony, and presenting to 

 the ear a pleasing combination. It has also been generally 

 understood, in all instruments capable of yielding har- 

 monics, that these latter decidedly harmonize with another 

 tone heard at the same time. If this were universally the 

 case, the term harmonic would be correct ; but having 

 recently noticed an important exception to the general 

 system of harmonics, I propose, in the present paper, to 

 substitute the term secondary tones, instead of the generally 

 adopted term. 



61 . When a musical glass, free from sensible interference, 

 (12, 49) is vibrated by the moistened finger, a note is pro- 

 duced which may be termed the fundamental tone of the 

 glass ; but by varying the force or manner of the pressure 

 of the finger on the periphery of the glass,"^ one, and even 

 two secondary tones can be elicited in succession, sometimes 

 concordant, but generally discordant in reference to the 

 fundamental note, and to each other. These tones would, 

 in musical language, be termed harmonics, but, in truth, 

 harmony is seldom produced. In one instance I have found 

 the secondary note to be C sharp, which remained always 

 the same, however the original fundamental note was 

 lowered by the addition to the glass of water or mercury, 

 (55, 56). In another instance, three tones were heard, the 

 lowest of which remained stationary, while the other two 

 varied according to the quantity of fluid in the goblet ; and 

 the intervals between the notes have varied from three semi- 

 tones to nearly, and sometimes beyond, an octave.f Thus, 



* The method of doing this I ifind it difficult to describe in writing. It is one 

 of those habits which practice alone can produce. 



t My respected friend, Mr. George Dodd, to whom I am considerably indebted 

 for kind and valuable assistance in procuring results to be stated in this and one 

 or two subsequent papers, has, within the last few days, informed me that if an 



