"K ^'"^'Ms of Liquid issuing from Circular Orifices. 289 



charges and small orifices, this inclination, and consequently the 

 variations in velocity and diameter, are insignificant in the part 

 of the jet we are considering, so that we should conclude that 

 the jet ought to be perfectly uniform ; nevertheless it resolves 

 itself into drops at a determinate point/' 



To these facts we may add another deduced from Savart's 

 experiments. When a jet issues obliquely upwards, within cer- 

 tain limits of inclination, the discontinuous part becomes scat- 

 tered in a vertical plane and forms a kind of sheaf. Now a 

 glance at the figure which represents such a jet in the plates 

 accompanying Savart's memoir, will show that the sheaf has its 

 origin very near the summit of the curvature of the jet, and con- 

 sequently at a point where the velocity, retarded from the orifice, 

 has not yet become sensibly accelerated. 



Thus, in the first place, in jets issuing horizontally under a 

 sufficient charge through orifices of small diameter, the discon- 

 tinuity first occurs at a point where the velocity is scarcely in- 

 creased, and consequently where the tension between two conti- 

 guous sections cannot have become considerable ; in the second 

 place, in jets issuing obliquely upwards under a sufficient charge 

 and through a suitable orifice, the discontinuity commences at a 

 point where the increase of velocity is still less ; and lastly, in 

 jets issuing vertically upwards, the discontinuity occurs notwith- 

 standing the retardation of velocity ; a retardation which, instead 

 of separating two contiguous sections, evidently tends to press 

 them closer towards one another. 



Although these reasons ought to be regarded as conclusive, 

 Magnus might nevertheless reply that neither Savart nor Hagen 

 state that the jets in question were protected from the small 

 efiects of vibrations proceeding from external noises, and from 

 the shock of the discontinuous part against the liquid into which 

 they fell. Now, according to Magnus, vibrations propagated in 

 a jet are a powerful cause of rupture, because by means of them 

 one section of liquid is drawn backwards, whilst the one imme- 

 diately preceding it is, on the contrary, pushed forwards. But 

 if so, then in ascending jets the rupture ought to take place at 

 the contracted section itself, that is to say, very near the orifice, 

 for there the jet has the least thickness, and the velocity of trans- 

 lation has. not yet suffered sensible diminution. In fact, at a 

 greater distance from the orifice, the increasing thickness of the 

 jet and the gradual diminution of velocity — from which latter 

 results, as I have remarked, a tendency of the sections to approach 

 each other — would render the rupturing action of vibrations more 

 and more difficult. = '\o ^aiitym^i a/It dM'^ *(Su<> ^ivm^f \^r» 



I have, however, repeated the. expe,riment of the sheaf ; first 

 by allowing full liberty to the small effects of external vibrations, 

 Phil. Mag, S, 4. Vol. 12. No. 79. Oct. 1856. U 



