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XXVII. On some Acoustic Plmnomena produced by the motion of 

 Liquids through short Efflux Tubes. By F. Savart*. 



THE memoir, an abstract of which we are about to give, is 

 a posthumous one, and was presented to the Academy of 

 Paris by Arago. Of the fom- paragraphs which the author 

 intended the memoir to contain, the first only was completed. 



When a liquid, such as water, issues through a cylindrical 

 efflux tube, it produces under certain circumstances musical tones 

 of great intensity and of a peculiar quality, somewhat analogous 

 to that of the human voice. The fact that this phsenomenon has 

 not been hitherto observed, arises from the peculiar circumstances 

 under which alone an efflux tube can occasion such tones ; for it 

 is necessary, fii'st, that its length should not differ much from its 

 diameter ; next, that the charges or heights of the issuing liquid 

 should bear a certain proportion to this diameter ; and lastly, 

 that the diameter of the reservoir should not exceed a certain 

 magnitude, dependent on the diameter of the efflux tube; in a 

 word, it is only under particular circumstances that the efiect 

 can exhibit itself in all its beauty. 



To obtain a general idea of the ph?enomenon, conceive one 

 extremity of a glass tube, from 6 to 8 centimetres in diameter 

 and 2 metres long, closed by means of a metallic plate, in the 

 centre of which is a circular aperture whose diameter is equal to 

 the thickness of the plate. After having fixed the tube in a 

 vertical position and filling it with water, the orifice is opened, 

 when it is observed that the efflux takes place periodically, and 

 is accompanied by a tone which at the commencement is feeble 

 and confused, but gradually acquires force as the charge dimi- 

 nishes, until it attains a certain limit, beyond which its intensity 

 decreases, and in some cases it disappears altogether. But as the 

 charge continues to sink, the tone soon regains force, becoming 

 at the same time more grave, until at length it attains another 

 maximum of intensity, after which it again becomes feebler in 

 order to increase anew, with a still lower pitch, and so on. 

 The number of these ventral segments, as they may be called, 

 depends upon the diameter and height of the tube, as well as 

 upon the diameter of the orifice. 



From the above it evidently follows, that when a liquid issues 

 through a short efflux tube, its whole mass is periodically subject 

 to certain modifications, cither in the velocity or the direction of 

 its component threads. 



The experimental analysis of these phajnomena presents great 

 difficulties, owing partly to their extremely short duration, par- 



* Abridged from the Comptes Rendus for August 1853, and communi- 

 cated by Dr. Hirst. 



