180 
Proceedings of the Royal Society of Edinburgh. [Sess. 
siphon is started, the sawdust is seen to be drawn in radially from all 
directions, and there is no cyclonic motion. Now repeat the experiment, 
but before putting the siphon in action give the water a circular move- 
ment. On now starting the siphon a quick circular, or rather spiral, 
motion will be seen round the outlet, and this quickly circling tube will 
be seen to develop downwards till it reaches the bottom of the vessel, 
where it will suck up the heavier particles of sawdust, the upward spiral 
current being densely packed with these particles, making the cyclone 
clearly visible, as represented in fig. 1, A.* After the cyclone has reached 
© 
Tig. 1 
the bottom of the vessel it continues to draw its supplies mainly from 
that part, as the velocity of rotation of the water there is less than 
elsewhere, partly owing to its being reduced by friction on the bottom of 
the vessel. 
It will be noticed that the cyclones in these experiments have a very 
small diameter, that the outflowing water surrounds itself with a quickly 
rotating tube of water, and that the outer water does not take much part 
in the action. This is greatly due to the outside water not being drawn 
nearer the centre owing to the intake being at the open end of the cyclone. 
Part of the smallness might be thought to be due to using a small pipe for 
the suction. This, however, does not seem to be the case, because we get 
the same small cyclones if we fix to the end of the siphon the wide- 
mouthed conical funnel C (fig. 1). This provides a large low-pressure 
* This experiment was shown at the meeting. 
