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IV. On Colliding Water-jets. 

 By H. Fkank. Newall, M. A* 



LORD RAYLEIGH has recently (Proc. R. S. vols, xxviii., 

 xxix. 1879, and vol. xxxiv. 1882) investigated many 

 of the phenomena of liquid jets. I will recall one form of 

 experiment, and record an observation and a few experiments 

 bearing on it. 



Two horizontal jets of water, issuing from similar glass 

 nozzles and fed from two glass bottles, are made to collide at 

 a small angle. When certain precautions are taken, such as 

 using clean and tolerably dust-free water, the jets rebound 

 from one another ; but they are made to unite if each bottle 

 is connected with the pole of a cell (such as Grove's or 

 Leclanche's). It is convenient to introduce a key. 



I have lately, in repeating this experiment, observed that 

 the colours of thin plates (Newton's Rings) are formed with 

 remarkable brilliancy between the colliding jets. The jets 

 are of circular section, but on impact they become flattened 

 against one another, so that the surfaces of separation are 

 more or less plane, and vertical. Between these surfaces, which 

 Lord Rayleigh has shown to be electrically insulated from 

 one another, there is a very thin film (of air, I presume) in 

 which the colours are visible. These afford a mode of obser- 

 vation by which one may possibly gain information as to the 

 nature of the action of electricity in determining the coales- 

 cence of the jets. 



I will first describe the appearance of the colours. The 

 case I have examined most carefully is that when the jets 

 start in the same horizontal plane and the surfaces of sepa- 

 ration of the colliding jets are vertical. There is some dif- 

 ficulty in getting a good view of the colours, on account of 

 the corrugations produced in the jets at collision. I have 

 found it best to take the plane of incidence of the light hori- 

 zontal, and to let the light fall against the direction of the 

 w r ater in the jets, and very nearly at normal incidence ; and 

 I use a magnifying- glass to observe with. 



The figure show^s the appearance of the jets about the place 

 of collision, the bold lines denoting outline and marks on the 

 near surface ; the dotted lines show the isochromatic curves : 

 those to the right are those which seem to be least distorted 

 by refraction. The bold lines at R show the small stationary 

 ripples on the cylindrical surface of the jet just before the 



* Comniimicated by the Author. 



