238 On the Sounds produced by a Jet of Water. 



height of the tone as the velocity of efflux increases^ as well as 

 a decrease in the height of the tone with increasing distance of 

 the plate. They do not, however, seem to justify the establish- 

 ment of the law just laid down. 



The author's view as to the origin of the notes is the same as 

 that given in his former experiments on the sounds of the jet of 

 air. He regards " the jet emerging from the aperture as a 

 moving rod which by friction against the edges and angles is set 

 in longitudinal vibrations, just like wooden rods and horsehairs 

 when drawn through the fingers •/■ and only that part has to be 

 taken into account which lies between the two rubbed parts. That 

 the jet acts as a special substance differing from the surrounding 

 medium, follows from the circumstance that the notes are not 

 formed merely when the jet issues into water, but also when it 

 flows into air. If the jet ascends in the air without sounding, 

 it is smooth and transparent like a glass rod; on the contrary, 

 when it sounds, it is rough and opake. 



For the experiments on the tones formed when water is driven 

 through apertures in thick plates the larger apparatus B was 

 used. Mere plates, of different thickness, gave no sound, what- 

 ever was the velocity with which the jet was driven through them ; 

 yet if the same plates, which to prevent their own oscillations 

 were made of lead, were cemented in tubes^ and the pipes thus 

 formed fitted water-tight in the apparatus, the water-tones were 

 produced in sufficient variety. The plate was generally at the top 

 of the tube, a few centimetres below the level of the water ; yet 

 with cylindrical or prismatic apertures the same notes were in 

 general formed, whether the plates were above or below. 



The tubes sounding by water sound generally also with air ; 

 yet it also sometimes happens that a tube will only sound with a 

 current of air, or, with a small aperture in a thin plate, with 

 a current of water. The tones with water are, generally speaking, 

 deeper and poorer than the air-tones. With increasing pressure 

 the air-tones frequently pass over to two or three, or frequently 

 more, harmonics, while the water-notes seldom make sudden 

 leaps with increasing pressure, but gradually become higher. 

 The greater steadiness of the water-notes may have its origin in 

 the particular length of the tubes used by the author, which, as 

 compared with the velocity of sound, is small. If the aperture 

 in the plate is conical, a note is only formed in case the current 

 passes in the direction of the widening of the cone. For water- 

 notes the widening of the cone must not be considerable, while 

 for air-tones this is to a certain extent advantageous. 



The results of these investigations agree in general with the 

 laws discovered by Savart. 



