.53 Causes of Water Spouts. 



This whirlpool, known in the country by the name of the gulf of 

 Soltenstroem is a true spout of air in water, of which the foregoing 

 experiment is a perfect representation on a small scale : and it may 

 be considered as demonstrated that the gulf is produced by a whirl- 

 pool formed at the bottom of a narrow and deep canal in which the 

 tide waters are compressed, while the surface is motionless ; for in 

 fact whatever rapidity may be given to a whirl at the surface of wa- 

 ter, the depression at the center will not increase in proportion to the 

 velocity, because the ascending central current continually replaces 

 the fluid expelled to the circumference ; but, when the rotation is 

 given to the water at the bottom, the replacement can take effect only 

 at the upper part of the axis, and of course the descending current 

 must form a gulf at the surface. 



On the same principle may be explained the fact that certain turns 

 in rivers, are dangerous to swimmers, for though no actual whirlpool 

 may be found at the surface, it is possible that a whirl at the bottom may 

 occasion a descending current not sufficient to produce a sensible de- 

 pression at the surface, yet rapid enough to affect the swimmer, whose 

 feet are near the center of activity. 



If in the last experiment the surface of the water be covered with 

 oil, the specific gravity of which being but little less, the descending 

 current may be produced by a much slower rotation. When it is first 

 fairly formed, the surface of the oil preserves its level. The water 

 precipitated at the centre draws in the thin stratum of oil which it 

 touches, and to which it adheres with a force not inconsiderable. 



When the surface of the oil begins to circulate, a depression is 

 produced, and a whirl of air is formed in the center which, however, 

 never descends to the bottom, whence it may be inferred that air has 

 less adherence to oil than to water. 



From the preceding facts, it is easy to perceive what must be the 

 result when instead of being produced on the surface of the water, or 

 at the bottom of the vessel, the whirl is found in the centre of the 

 liquid column. Two opposite currents are then formed, one ascend- 

 ing and the other descending, which are carried along the axis to the 

 centre of the primitive whirl. 



Fourth Experiment. — I placed diagonally in the vessel a small 

 glass rod, with the inferior end drawn to a point, and fastened it into 

 a groove fixed to the circumference at the bottom ; the other end was 

 aupported on the opposite edge of the vessel- 



