1882.] 



On Liquid Jets. 



131 



be connected with the hardness of the Cambridge water — at home I 

 had nsed rain water — I repeated the observations with distilled water, 

 but without finding any explanation. The jet of distilled water 

 scattered freely, both with and without soap, and could only be pre- 

 vented from doing so by electricity. Eventually the anomalies were 

 traced to differences in the character of the soap. That used at 

 Cambridge up to this point was a clarified specimen prepared for toilet 

 use. On substitution for it of common yellow soap, the old effects 

 were fully reproduced. 



Further experiment seemed to prove that the real agent was not 

 soluble soap at all. If water impregnated with the yellow soap was 

 allowed to stand, a white deposit separated, after which the super- 

 natant liquid was found to be inactive. But after shaking up the 

 same effects were produced as at first. The addition of caustic potash 

 to the unclarified soapy mixture destroyed its power. On the other 

 hand, sulphuric acid rendered the clarified soap solution active. 



The natural conclusion from these facts would be that the real 

 agent is unsaponified greasy matter distributed through the liquid ; 

 and this view is confirmed by the striking results which follow the 

 addition of small quantities of milk. The experiment may be made 

 conveniently by connecting a Woulf's bottle with the water tap by a 

 rubber tube fitted to one tubulure, while the vertical nozzle is in con- 

 nexion with another tubulure. If a little milk be placed in the bottle, 

 the jet of opalescent liquid apparently coheres, and passes the 

 summit in one unbroken stream. After a time the milk is gradually 

 washed out, and the scattering is re-established. About one drop of 

 skimmed milk per ounce of water is sufficient to produce the effect. 



I must not omit to mention that on several occasions distinct 

 evidence was obtained that it is possible for soap to be in excess.. 

 With a large quantity the coherence of the jet was imperfect, and was 

 improved by dilution. The complete elucidation of the subject pro- 

 bably requires more chemical knowledge and experience than is at my 

 command. 



Of the various other substances which have been tried, such as 

 glycerine, sugar, gum arabic, alcohol, sulphuric acid, none have been 

 found active. 



Vertical fountains of mercury were found not to scatter. The head 

 was about 15 inches, and various glass nozzles were used from inch 

 to inch in diameter. Also a nozzle terminating in an amalgamated 

 brass plate, through which a hole of inch was pierced. In all 

 these cases the drops of mercury coalesced at collision, behaving in 

 the same way as drops of milky water issuing from the same nozzles. 

 Fountains of clean water issuing from these nozzles under the same 

 pressure scattered freely. 



When the diameter of the nozzle from which a water jet issues is 



k 2 



