174 Prof. Magnus's Hydraulic Researches. 



cular openings, show a similar behaviour, as far as I have been 

 able to observe them. 



The higher portion of the stream is smooth ; and its diameter 

 diminishes only very gradually to a. From « to /3, where it 

 commences to become turbid, separate contractions appear. The 

 parts of the jet between these assume more and more a sphe- 

 rical form, Finally, the rounded masses separate and form di- 

 stinct drops of various size and form, which follow one another 

 irregularly. 



157. The separation of the jet into distinct masses occurs, 

 therefore, in precisely the same manner as is described by M. 

 Plateau in the second series of his excellent investigations, 'Sur 

 les figures d'cquilibre d'une masse liquide sans j)esanfeur^. 



158. The regularity with which the individual masses form 

 and separate is, however, not very great. I imagine the cause 

 of this to be, that at the considerable distance from the efflux- 

 orifice at which the contractions begin, the velocity of all parts 

 which lie in the same section (at right angles to the axis of the 

 stream) is no longer the same. Hence also occur sometimes the 

 very small drops which move laterally. The smaller the efflux- 

 orifice, the greater is the number of these drops which are formed. 



Appearance of a jet with swellings when observed by means of the 

 fine slit. 



159. The appearance of the jet is quite otherwise when swell- 

 ings occur in it. It is true that the upper continuous por- 

 tion appears smooth to the naked eye, and even by help of the 

 rotating disc, swellings can scarcely be recognized in it ; but on 

 employing the rotating mirror, we may convince ourselves, as has 

 been already mentioned in § 146, that it has alternating greater 

 and smaller diameters. It is very surprising, on employing the 

 mirror, to see how the broad, luminous, smooth band shown by 

 the stream as long as it has no swellings, immediately appeal's 

 notched as soon as a struck tuning-fork is placed on the stand, 

 or as soon as the magnetic hammer is set in action. 



Inasmuch as the swellings or diflferences in diameter of this 

 part of the stream, especially at a small distance from the orifice, 

 are so inconsiderable as not to be recognizable by means of the 

 rotating slit, it is not possible to represent them in the drawing. 

 Viewed, however, through the rotating slit, the swellings appear 

 as they are represented in fig. 12. Above the first swelling at 

 /3, very small excrescences a])pear, which gi-adually increase in 

 size. Their forms are very regular throughout. Shortly before 

 separating as distinct masses from the stream, they are only 

 connected by very narrow masses of water, which appear like 

 * Taylor's Scientific Memoirs, vol, v. p, 586. 



