Causes .of Water Spouts. 51 
it may then be regarded as a certain fact that an ascending cur- 
rent takes place along the axis of all whirlwinds, which are formed on 
the surface of liquids. 
But this current would become descending if the whirl, instead of 
forming itself on the’surface of the liquid, was excited at the bottom 
of the vessel, because in this case, the fluid driven by the centrifu- 
gal force could be replaced only at the superior extremity of the 
axis of the whirl; the following experiment will demonstrate this 
truth. 
Third Eeiisedd=i adjusted the mill at the bottom of the ves- 
sel of water (Fig. 2.) and turned it by a mechanism which left it to 
act freely, as an inspection of the figure will show. There was soon 
formed a depression at the center of the surface of the water of the 
shape of a small funnel; and continuing the movements, the apex of 
the funnel or inverted cone of air which filled.it, was perceived to 
extend itself by degrees, and approach the mill: bubbles of air were 
separated from this point, which descended rapidly to the bottom of 
the vessel; and at length when the rotary movement had acquired 
the ordinary velocity, a regular column of air extended throughout 
the axis and entered among the vanes of the mill occasioning a regu- 
lar whistling sound. 
This whirlwind was pointed below like a spindle, and the air di- 
vided into bubbles escaped from the mill and rose rapidly along the 
sides of the vessel. Light bodies, placed on the surface of the wa- 
ter, such as cork, and small bits of paper, after revolving within the 
gulf, were soon carried down to the bottom, whirling round with ra- 
pidity, as they descend, until they reach the mill, whence they rise 
along the sides. By regulating the movements, they may be retained 
at different depths as long as may be desired. 
* This experiment explains an extraordinary phenomenon which 
regularly occurs on the coast of Norway. ‘ When the tide is ri- 
sing,” says Mr. De Buch, “the ebb and flow are compressed within 
narrow passages; the water turns in whirlpools the violence of which 
draws to the bottom boats which approach them; the unfortunate 
fishermen cling to their boats. Sometimes the whirlpool throws to 
a great distance both men and boats, but often they are swallowed 
up.’ * i 
* Travels in Norway and Lapland, by M. De Buch. 
