132 PHYSICAL PHENOMENA OF UPPER REGIONS OF ATMOSPHERE. 



It might be supposed from this that equatorial repulsion only can be 

 produced by such a revolving sphere ; but the complexity of cyclonic 

 movements baffles our most assured expectations. If we bring near 

 the sphere a light ball, it is strongly attracted and commences to turn 

 rapidly about the moving sphere in the equatorial plane. A second, 

 a third, launched in the same way, follow it with varying velocity and 

 represent satellites. The planetary similitude is then complete. 



This paradox of a repulsion changed into attraction by changing the 

 form of the body presented is easily understood when we consider the 

 resultant of the attractive and repulsive forces on the surface of the 

 movable body. Cyclonic attraction dominates throughout a greater 

 angular extent around the revolving sphere. This can be easily proved 

 by placing below the sphere a basin full of hot water. If the air of the 

 room is quite calm, we see the steam gradually unite into a whirling 

 column extending from the surface of the water to the revolving sphere. 

 This is an imitation of a waterspout. The importance of this phe- 

 nomenon has led M. Weyher to reproduce it in a more striking form, 

 using a much greater amount of mechanical energy, corresponding 

 more nearly to that which occurs in nature. 



The gyratory movement, which in nature has its source in the upper 

 regions of the atmosphere, is set up by a fan placed three meters above 

 a vessel of water 4 meters in diameter (fig. 2, PI. I). When the fan is 

 made to revolve (400 to 500 revolutions per minute) the aerial cyclone 

 thus formed reaches gradually the surface of the water, which is seen 

 to be agitated, forming centripetal spirals that unite in a cone several 

 centimeters in height. Above this cone there forms a sheaf of droplets 

 that fall back with a whirling motion. This attraction at a distance is 

 rendered still more striking when the water is slightly heated. The 

 steam then forms a hollow tube, the empty part of which is distin- 

 guished by its dark tint and its geometrical regularity. It passes from 

 the surface of the water toward the fan, raising light objects like bits 

 of straw that float on the liquid. 



Such is the experiment that was made in the open air at the works 

 of the Societe Weyher et Eichmond in 1887. With the smaller appa- 

 ratus which you see here dig. 3, PI. I) we can repeat it under equally 

 conclusive conditions. The fan is placed at the upper part of this case, 

 which is 2 meters high and provided with a glass front. The water, 

 slightly heated and containing a little soap, is placed in a basin at the 

 bottom of the case. As soon as I set the fan going you observe the 

 agitation of the water, the soap bubbles rushing toward the foot of a 

 column of steam. Soon that column takes on the form described above 

 and simulates exactly the appearance of a natural waterspout. Below 

 we see the "bush" — that is to say, the sheaf-like arrangement of bub- 

 bles; above, the hollow funnel of steam. A light ball placed on the 

 surface of the water is first drawn toward the center of disturbance 

 and caught at its foot. By increasing the velocity of rotation (which 



