1836.] Observatiom on Visible Vibration, 131 



and I should observe, that the existence of the very high E 

 flat (marked 5) is somewhat doubtful. 



70. In a recent visit to London, Mr. Dodd was so kind 

 as to accompany me to the large hour bell of St. Paul's 

 Cathedral. Our observations produced similar results, but 

 the very inconvenient footing among the rafters of the 

 belfry, the noise of the busy world below, and the great 

 thickness of the metal (ten inches) all militated against 

 accurate observations, and differed much from the monastic 

 stillness of our former serial observatory in the tower of 

 Salisbury Cathedral. As far as we could perceive, the rela- 

 tive distinctness of the tones was not much varied by strik- 

 ing on different parts of the exterior surface ; but the major 

 third and the major fifth were always perceptible, while 

 the tone of the grave harmonic was of so vast and splendid 

 a character* that it was difficult to determine to what octave 

 it belonged. 



71 . We also remarked a curious instance of interference. 

 When the bell was struck with the palm of the hand 

 frequently and at regular intervals, one note seemed to 

 prevail ; but when a sudden blow was given at a smaller 

 interval of time, the isochronism of the vibrations was dis- 

 turbed, and the product was a note two whole tones higher 

 than before. 



72. The two smaller bells which chime the quarters have 

 for their fundamental tones E and A, with the secondary 

 tones G sharp and B ; and C sharp and E. Immediately 

 after the quarters have chimed, these bells afford a fine 

 example of interfering sounds ; the intervals of silence 

 being well marked and distinct. These intervals cannot, 

 however, be considered to owe their origin to the causes 

 before stated (12), but to certain systems of undulating 

 circles of air, meeting and combining. 



* The German student will not fail to remember the immortal production of 

 Schiller, " Das Lied von der Glocke." 



" Von dem Dome, 

 Schwer und bang, 

 Tont die Glocke 

 Grabgesang." 



*'■ Vom reinlichen metalle. 



Rein und vol! die Stimme schalle.'* 



k2 



