EXPERIMENTAL ANALOGIES TO ATMOSPHERIC MOTIONS 
a few inches in length was mounted eccentrically and 
rotated about the central axis of a large cylindrical 
container. A vortex was generated along the central 
axis with outflow at the wire end and inflow at the 
opposite end of the container. The motions were fol- 
lowed by means of burnt lime in the water. 
All sorts of modifications of this experiment have 
since been made. Some investigators have used mechani- 
cal means, such as fans or other devices, for generating 
the vortex in both air and liquids. In this group were 
Andries [5], Hirn [82], Dechevrens [13], Weyher [45] 
(Fig. 2), and Dines [15], all in the last two decades of 
TAL ATL GATS | ETAT 
sake Nis cil 
Fic. 2.—Engraving of a tornadolike vortex produced by 
Weyher in the open above a large basin of water. The fan at the 
top produces the motion. (After Mascart [45].) 
the 19th century, and Hale and Luckey [30], Exner [17], 
Lunelund [43], and Letzmann [41] (an extensive work 
on air vortices) since 1900. Others have investigated 
the vortices produced by mechanical removal of fluid 
in a field of gentle, initial rotation (the bath-tub drain 
experiment), for example, Aitken [8, 4] between 1900 
1237 
and 1918, Letzmann [40] who worked with water in 
1927, and also some others of the previous group. Among 
those who have investigated the vortex motions in- 
duced by the “secondary flows” associated with fric- 
tion, especially where angular accelerations of the entire 
system are involved, are von Bezold [8] and Belo- 
polsky [6, 7] in the latter part of the nineteenth century 
and Ahlborn [1] in 1924. The final group are those who 
have worked with thermally generated motions pro- 
ducing either isolated vortices or more complex fields of 
rotational motion. This group includes Vettin [67-69] 
(Fig. 5) and Czermak [12] (Fig. 3) before 1900, and 
Fic. 3.—Photograph by Czermak of a convective column in 
a motion similar to those described by Oberbeck [47]. The 
water in the beaker is gassed-out and allowed to come to com- 
plete rest. Heating at the bottom of the beaker is produced 
electrically by a spiral of fine platinum wire 6 mm in diameter. 
Note the delicacy of the vortex motion at the cap. Czermak 
also investigated the effect of stratification on these motions. 
(After Czermak {12].) 
Aitken [8], Exner [17], Sipinen [59], and Terada and 
Hattori [65], between 1915 and 1926. (Summaries of 
most of the above-mentioned investigations and other 
similar ones are given in [11] and [70].) 
It is difficult to sum up the net significance of all this 
work with respect to the problem of the cyclone or even 
the tornado. Many curious and beautifully well-de- 
fined phenomena are discussed in these studies, but 
their actual implications for the questions which, in 
most cases, they were specifically intended to illuminate 
