SCIENTIFIC NEWS. QW 



number is to that of the vibrations of another slip of metal, 

 taking- place at the same time and under the same circum- 

 stances, in the inverse ratio of the squares of their lengths. 



In this part too Mr. Chladni treats of the temperaments Tempera- 

 proposed by different persons. He prefers that adopted by in "" u - 

 Kameau, which renders the 12 semitones included in the 

 octave perfectly equal to each other, by making them an- 

 swer to 12 geometrical mean terms between the two ex- 

 tremes. 



In the <2d part we find the author's discoveries. Fie first Rods have 

 examines the vibrations of choids and rods, and distinguishes !* 1ree ^ ftt ; rcnt 

 three sorts, the transverse, longitudinal, and those which he tion,produciog 

 calls gyratory. The first take place when a chord or rod is different notes, 

 struck in a direction perpendicular to its length. But a 

 rod, that would produce a certain note when thus struck/ 

 would emit a very different one, if rubbed with a piece of 

 cloth in the direction of its length. If the rod be of glass, 

 the cloth must be wet; if of any other substance, dry. 

 These vibrations, which he terms longitudinal, he has found 

 subject to the same laws in a solid rod, as the longitudinal 

 vibrations of tlie air in an organ-pipe; and he lias given a 

 table of these vibrations for different substances, such as 

 glass, metal, and wood. 



Notes still different from those emitted in the two pre- 

 ceding circumstances are produced, when a rod is rubbed 

 in a direction very oblique to its axis. Mr. Chladni gives 

 the epithet of gyratory to the vibrations resulting from this 

 kind of friction, because he supposes, that the particles of 

 the substance acquire a movement of rotation or oscillation 

 round its longitudinfd axis. He says he has found, that in 

 these vibrations the numerical ratios are the same as those 

 of the longitudinal vibrations, but that the tones of each 

 rod are a fifth higher. 



Each series of inquiries abovementioued has been made Experiments 



with rods fixed at each end, merely supported at one or nuK,e wllh 



i.i •° u rix '' d in 



both ends, fixed at one end and supported at the other, and different ways. 



loose at each end. Each of these circu instances occasions 

 a difference in the results. Mr. Chladni lias likewise exa- 

 mined trTe*vibrations of curved rods, forks, and rings. Eu- 

 l'er applied the last species of vibrations to the phenomena 



of 



