Causes of Water Spouts. ~~ fe 
brings with it all the vapors that are above toward the centre of the 
primitive whirlwind. 
us, in the fourth experiment, (Fig. 3.) the descending spout of 
oil, and the ascending one of blue dust, mingle in the zone which 
passes through the centre of the mill. In ascending spouts, below 
the clouds, the spectator can see only half the phenomenon, as the 
other half passes above the clouds; by this mechanism, the lowest parts 
of the atmosphere and those which are elevated above the clouds, 
are drawn to the same point by the two opposite interior currents of 
the spouts ; these strata of air, charged with vapour and often with a 
different kind of electricity, unite, and produce the thunder and other 
effects which sometimes accompany water spouts. . 
In descending spouts, the spectator sees the entire phenomenon, 
because the whirl which produces it, is formed between the clouds 
and the sea. 
The water, under descending spouts, is generally seen to rise and 
boil, even while the aérial current isstill far from the sea ; sometimes 
the two spouts join and form but one; the primitive whirl is then at 
the point where they join; but if they remain separate, it is because 
neither the one nor the other reaches the primitive and invisible whirl- 
wind which produced them. 
One circumstance in the 2d experiment presents another asiariet 
able analogy ; it has been seen that sand produces an empty spout, 
into which clouds of fine sand are gradually forced ; similar observa- 
tions of empty spouts have been several times made by travellers, 
who always represent them as opaque on the borders, and transpa- 
rent in the middle.* Jn a description cited by Mr. Berthollon, se- 
* What is the force which retains the particles of sand and water in the regular 
circle in which they revolve as rapidly as if they had a centre of attraction? The fol- 
lowing explanation may, I think, be given, both as to the imitative experiment, or 
the natural Line enon. 
of the surface can issue from the circle which it traverses without be- 
pe repsed now the eurtace of = spon soothing curcagnoat its height, the same 
this ‘aitinn’ is then retained by the pressure of the lateral columns. , 
The replacement cannot take place in the interior of the spout except at the infe- 
rior end of the. axis, which is not submitted to the centrifugal force, and an equili- 
brium is there established, between the energies of the centrifugal force, and the 
weight of water withdrawn, and which determines the diameter of the spout. 
res 1 # ty 1 28 As ies t6 fa OK shine of 
have the regular and cylindrical form of the first, but rather that ofa spindle or of a 
cone o ing t a | 7 ds, le « ting i point +h bot ere 
sé, 
ivr, 
