PHYSICAL PHENOMENA OF UPPER REGIONS OF ATMOSPHERE. 133 



increases the power of the cyclone) the ball is raised by the waterspout, 

 sometimes following the funnel throughout its entire height. 



The helicoidal movement of this light ball, as well as the appear- 

 ance of the nebulous funnel, show very well how the waterspout is 

 formed. We can see the whorls of helicoidal currents superposed on 

 each other, some going up, others going down. There is a perpetual 

 passing and repassing between the fan and the surface of the water. 

 As all the currents turn in the same direction, if those going up describe 

 right-hand helices, those going down describe left-hand helices. It 

 is the failure to recognize this double movement of ascent and descent 

 that has kept up the misunderstanding between the partisans of the 

 ascending spouts and those who claim that they are always descending. 



The ascensional movement of the light ball drawn into the spout 

 shows the upward velocity very well. It is more difficult to demon- 

 strate the downward motion, which some theorists consider the only 

 one, because the space in which it acts when the experiment is shown on 

 this reduced scale is quite contracted, being confined to the very interior 

 of the nebulous envelope, where a dark color shows a central cavity. 

 Still I shall be able to demonstrate this movement by means of a very 

 simple device. I place at the upper part of the spout a body that emits 

 smoke. We see that this smoke is soon drawn iuto the spout, is twisted 

 into a long, pointed cone, and descends toward the surface of the water. 

 This is exactly what is seen in nature when in a marine waterspout 

 the clouds descend in the form of a funnel that attaches itself to the 

 "bush" formed by the water on the surface of the turbulent ocean. 

 This funnel might be called the safe portion of the spout. The danger- 

 ous part is invisible, being the envelope of air that whirls about this 

 funnel. In the experiment you see before you the reverse is the case. 

 The cyclonic envelope is quite visible, thanks to the steam that has 

 been supplied. The internal funnel remains dark. By introducing the 

 smoke we verify its existence and form. 



I could proceed to show you that with a similar apparatus it is 

 possible to reproduce a cyclone with all its peculiarities. The varia- 

 tions of pressure at the time of its passage — the low barometer, the 

 central calm, the sudden outburst of the wind, the eye of the storm, 

 etc. — all these M. Weyher has demonstrated. But time is wanting. 

 The experiments you have just seen will suffice, I hope, to show how 

 complete these experimental syntheses are and how they reproduce 

 natural phenomena even in the most minute details. 



I will conclude by merely calling your attention to the great gain, 

 both in extent and certitude, that must accrue to meteorology by its 

 becoming an experimental science. 



