M. A. Kundt' a Acoustic Experiments, 41 



I am informed by Mr. Barnes that, in one locality in Cape 

 Breton, gypsum is found containing titaniferous iron-sand; 

 hence we may expect that, among the numerous sulphate-of- 

 calcium deposits of the province, considerable difference will be 

 found in the nature of their accessory minerals. 



III. Acoustic Experiments. By A. Kundt*. 



nPHE great intensity with which the longitudinal tones of 

 A rods and tubes act upon our ear, and which is sometimes 

 unbearable, though it may be partially explained by greater sen- 

 sitiveness for high tones, has undoubtedly its origin in a violent 

 agitation of the air. But as, more especially in the case of open 

 tubes, the terminal surfaces which transmit their motion to the 

 air are generally of small extent, the question arose as to the 

 manner in which the transversal vibrations cooperate with the 

 longitudinal vibrations, simultaneously with which they are 

 formed. 



Hence, at various parts of longitudinally vibrating rods and 

 tubes, M. Kundt tried to set membranes and similar bodies in 

 vibration by the transversal vibration of the air. The intensity 

 in different places was also investigated by moving close over the 

 surface of the tube one end of a caoutchouc tube, the other end 

 of which was held in the ear ; this is a method by which nodes 

 and loops may be investigated in the case of transversely vibra- 

 ting bodies. 



The result was that at the sides of longitudinally vibrating 

 bars or tubes no motion of the air could be demonstrated, and 

 it was only perceptible at the ends, but there it had great inten- 

 sity. Hence a bar clamped at the ends and set in longitudinal 

 vibration would be incapable of communicating its motion to the 

 air, and would therefore remain inaudible to us. 



These experiments led M. Kundt to further interesting inves- 

 tigations. 



Weber (Schweigger's Ann. vol. liii. p. 308) observed that 

 a cork, which fitted one end of a glass tube several feet in 

 length, moved from the end to the middle when the tube was 

 held horizontally and rubbed; this was the case even when the 

 tube became slightly narrower towards the middle, and also if, 

 while the tube was held vertically, a column of water a few cen- 

 timetres in height rested on it. 



M. Kundt made the experiment with a cork ring placed on 

 the tube, and found that the ring sometimes moved from the end 



* Translated from the Fortschritte der Pkysik for 1865, being an abstract 

 of papers in the Berliner Monatsberichte and in Poggendorff's Annalen. 



