NATURAL PHILOSOPHY. 135 



the second ; for the part of the tubes exposed to the sun was con- 

 siderably greater than that in contact with the cold ground. 



The interior being filled with water and completely freed from 

 air, experiments were made on the velocity in water. The 

 shock was produced by suddenly forcing in the piston of a hy- 

 draulic press. However rapidly the pump-lever was lowered, 

 no shock, properly so called, was produced, but a gradual com- 

 pression ; thus the indication of the style upon the register, in- 

 stead of being a well-defined zigzag, as in the case of air, traced 

 an elongated curve, of which the point of coincidence with the 

 spiral inscribed by the style at rest was difficult to determine. 



Four successive experiments gave a mean of 345 vibrations of 

 the tuning-fork between the initial and return shocks. The 

 length of the conduit between the two plates which closed the 

 extremities was 603.25 metres ; hence the distance travelled by 

 the compression between departure and return was 1,206.5 

 metres. The temperature of the water at the top of the conduit 

 was 20, and 13 at the bottom. The temperature of the sur- 

 rounding air was 18. Under these circumstances the velocity of 

 the compression was found to be 897.80 metres per second. 



Wertheirn deduced from the sound given by brass organ-pipes 

 dipping in water, 1,173 metres per second as the velocity of sound 

 in water. This number is much less than 1,435 metres per 

 second, found by M.M. Colladon and Sturm, in direct experi- 

 ments made on the Lake of Geneva. 



The value which M. Andre found is still further from the 

 number observed in an indefinite mass of water. 



The author calls the attention of physicists to the influence which 

 the elasticity and friction of the containing sides may have on the 

 propagation of a shock in the midst of an almost incompressible 

 fluid. 



FIXED NOTES CHARACTERISTIC OF THE VARIOUS VOWELS. 



BY 31. R. KOENIG. 



" According to the researches of MM. Donders and Helmholtz, 

 the mouth, arranged for the emission of a vowel, has a note of 

 stronger resonance, which is fixed for each vowel, whatever may 

 be the fundamental note on which it is given. A slight change 

 in the pronunciation modifies the vocal notes so sensibly that M. 

 Helmholtz has been able to propose to linguists to define by these 

 notes the vowels belonging to the different idioms and dialects. 

 Hence it is of great interest to know exactly the pitch of these 

 notes for the different vowels. M. Donders sought to arrive at 

 this by observing the rustling or whistling which the current of 

 air produces in the mouth when the different vowels are whis- 

 pered; the notes which he has found differ considerably from 

 those given by M. Helmholtz. The latter used a set of tuning- 

 forks, which he made to vibrate in front of the mouth when it was 

 arranged to articulate a vowel. Every time the sound was 

 strengthened by the air enclosed in the cavity of the mouth, this 

 mass of air was evidently in unison with the tuning-fork. By 



