-—. Causes of Water Spouts. 
It is very remarkable that the little central column had a rotatory 
movement more rapid than the mill which produced it. The larger 
fragments of copal, as also drowned flies, were raised with difficul- 
ty and ascended more slowly, following a less elongated helix, which 
brought them within a short distance of the central column, around 
which they revolved like satellites. 
When the spout had raised all the copal sitet’ in the center of 
the bed at the bottom, the particles were observed to detach them- 
selves by degrees from the circle, pass to the center to form the spout 
and thus the process went on until the bottom was quite cleared and 
the whole mass was in motion. In stopping the mill at this point, all 
the powder became — in the center in the form of a regu- 
lar cone. 
I varied the experiment by substituting smalt or ihe blue glass of — 
cobalt of great fineness, and with the same result; the spout which 
was formed had the appearance of a blue silk serine and was thinner 
by half than that of the copal. 
The formation of the spout depends less upon the specifi ight- 
ness of the powder than its fineness ; with an equal movement, the 
pulverized smalt was raised more easily than the coarser copal. The 
diameter of the spout ‘depends also upon the degree of coarseness of 
the particles of dust which form it, the blue glass produced a spout 
of three lines in diameter very regular, whilst in the same vessel and 
with the same mill, fine sand formed a spout an inch and a half in 
diameter ; and what is very remarkable the last was interiorly empty 
and had the form of a tube, opaque on the borders, and transparent 
in the middle: in slackening and hastening by turns the movement, we 
see as it were clouds of very fine sand in agitation in the interior ; 
in mixing this sand with pulverized smalt we distinguish two spouts 
one within the other, the exterior formed by a tube of sand and the 
interior by a column of blue glass less regular. 
The cause of these various movements may be easily explained, if 
we observe that when the whirlwind is found on the surface of a li- 
quid, the centrifugal force drives it toward the circumference and oc- 
casions a depression at the center; the equilibrium thus destroyed 
cannot reestablish itself but by the axis of the whirl, which is not sub- 
ject to the centrifugal force : the liquid then rises in this part, press- 
ed by the lateral columns which are higher, and being in its turn in- 
cessantly driven to the circumference, a constantly ascending current 
is established in the axis of the whirlwind. 
