102 Mr. G. F. Rodwell on some Effects 



the returning streams, and ended at the ascending jet ; within 

 these parabolic currents the particles of lycopodium were ob- 

 served to revolve in ellipses moving in contrary directions. Par- 

 ticles of lycopodium rose into that portion of the two descending 

 streams most remote from the ascending jet, and revolved in 

 ellipses moving in opposite directions, the major axis of each 

 ellipse being parallel to the descending stream. The particles 

 in each elliptic current revolved in a direction opposite to that of 

 those which revolved in the ellipse (within the parabolic current) 

 nearest to it. In fig. 3, A represents the ascending jet, B B the 

 returning streams, C C the parabolic currents on the water- 

 surface immediately beneath them, and D the central surface- 

 current induced by the lateral action of the ascending jet. 



The jet A ascends until it is stopped by the adhesion of the 

 substance of the vessel, it then returns by the two parabolic 

 streams B B. Now these returning streams tend, on entering 

 the liquid mass beneath them, to produce the same currents 

 which we have seen (from the first experiment) to be produced 

 when a stream of liquid enters a liquid mass at right angles to 

 its surface. But particles of water are hurrying towards D to 

 supply the place of those which are perpetually dragged from 

 the vessel by the lateral action of A ; hence the currents which 

 would otherwise proceed in straight lines from the points at 

 which B B enter the fluid are caused to curve round to the point 

 from which A issues. 



Many very beautiful effects may be produced by allowing a 

 jet of water, capable of rising to the height of about a metre, to 

 impinge upon the edge of a vessel. The jet, more or less re- 

 strained by adhesion, breaks up into numberless globules of 

 water following a great variety of curved paths. 



When a jet of water is allowed to escape just beneath the 

 surface of water upon which lycopodium has been scattered, 

 the currents produced at right angles to the axis of the jet are 

 rendered very apparent by the rapid rush of lycopodium into 

 the ascending jet. The particles are carried away by the jet, 

 and in this manner a large surface of water maybe entirely freed 

 from lycopodium in the course of a few minutes. 



One of Venturis first experiments on lateral action was that 

 in which he caused a stream of water to flow through a vessel 

 containing water, and to escape above its level, by which means 

 the water speedily sank to the level of the stream. A jet of 

 water delivering, say, 100 cub. centims. per minute may be caused 

 (by allowing it to escape nearly vertically several millimetres be- 

 neath a water- surface) to remove far more than its own volume 

 of water from the vessel. The quantity removed obviously de- 

 pends entirely upon the velocity of the issuing jet : cNirrents are 



