1240 
the large horizontal extents involved and the importance 
of vertical turbulence. The experimental results here 
need to be extended so that some numerical similarity 
comparisons can be made. 
Experiments on the General Circulation 
Historically, the principal investigations which have 
proceeded with the general circulation problem in mind 
are those of Vettin [67-69] between 1857 and 1884, 
Exner [17] in 1923, and Ahlborn [1] in 1924 (see also the 
work of Rossby [90, 50] in 1926 and 1928). Vettin 
performed an extremely interesting series of experiments 
on convectional flows in rotating and nonrotating sys- 
tems. The most important from our present standpoint 
utilized a rotating disc of air. In one case he placed ice 
at the center of the dise (Fig. 5) and obtained relative 
i=<HW , 
S. 
S PTT | 
SS os 
Fig. 5.—Idealized average relative circulation of air in a 
slowly rotating disc with a cold source at the center. Diameter 
1 ft, height 2 in. approximately. The sharp disagreement with 
results in a dise of water of about the same height-diameter 
ratio (see Fig. 11) shows that extreme care is necessary in 
interpreting the mechanisms responsible for such motions. 
(After V ettin |69].) 
circulations corresponding with what has become the 
traditional picture of the trade-wind cell. With the 
same apparatus, using air again as the medium, he 
provided a small gas flame arranged so as to heat the 
same point on the rotating base plate. This generated 
well-defined vortices within the air, accompanied by 
average relative circulations. 
Vettin had the disadvantage in 1857 of writing before 
any clearly developed theory of dimensional or model 
analysis had been formulated. He attempted to draw 
sweeping meteorological conclusions from his work and 
LABORATORY INVESTIGATIONS 
was consequently criticised very severely by Dove 
[16], who was one of the prominent meteorologists of 
the time. Certain of the experimental phenomena 
which Vettin attempted to imterpret meteorologically 
were trivially, if at all, related to the atmospheric 
case, but Dove’s criticisms, on the other hand, were 
oversevere. In fact certain of the ideas which Vettin 
derived from his experiments, for example, those 
regarding the steering of storms, are more nearly in 
accord with the facts than the objections which Dove 
raised against them.’ 
Exner’s experiments [17] nearly three-quarters of a 
century later were almost identical in one phase with 
Vettin’s except that he used water. (However, Exner 
included the air vortex study mentioned earlier.) He 
placed a thin cylinder of ice, dyed with an ink, at the 
center of the rotating pan of water. The cooled portions 
of the water were consequently colored and could be 
seen spreading out along the bottom in tongues, as 
seen in Fig. 6. Systems of vortices, which Exner stated 
Fig. 6.—Photograph from above of Exner’s experiment with 
tongues of ice water (colored) spreading along the bottom from 
a center cylinder of ice and developing vortices along their 
edges. Exner states the circulation in the cold water to be 
easterly on the average. (Rotation counterclockwise, periods 
3-7 sec; diameter of pan 1 m, height of water 4-6 cm; gas flames 
at edge; camera rotating with pan.) (After Hxner [17].) 
to be not unlike a polar-front cyclone family in appear- 
ance, developed along their boundaries. The mean rela- 
3. The whole affair ended in a rather curious and interest- 
ing way. Vettin did not publish anything further for 27 years— 
until persuaded to do so, apparently by friends. In a note to the 
article which Vettin finally wrote in 1884 [69], in the first vol- 
ume of the Meteorologische Zeitschrift, W. Képpen says the 
following, after mentioning that Dove’s ‘(Law of Storms” also 
appeared in 1857: “‘Dove, der sich durch dusserst umfassende 
Literaturstudien und mit Hiilfe einer lebhaften Phantasie, 
aber mit wenig eigenen Beobachtungen, ein scheinbar in sich 
abgeschlossenes Bild um den grossen Bewegungen der Atmos- 
phire entworfen hatte, wandte sich gegen den kiihnen Hin- 
dringling in das von ihm beherrschte Gebict ...mit einer 
Abweisung von schwer verstindlicher Heftigkeit . . . Wir diir- 
fen hoffen das die Zeit ...giinstiger...ist, und das die 
Hinfiithrung des Experiments in die Meteorologie nicht mehr 
als Kinderspiel sondern als ein Gegenstand von héchster 
Bedeutung anerkannt werden wird... .” 
