750 
arising from the cyclonic gyrations, especially 
where surface friction is great’? (‘A Popular 
Treatise on the Winds,’ pp. 338-339). This is 
from Ferrel’s latest book, and note that he says 
the increased pressure ‘is independent of the 
gyrations.’ He explains that the velocity, v, of 
the air circulation tends to decrease the pres- 
sure at the center of the cyclone and not at the 
same time cause a rise of pressure, as is as- 
sumed by Professor Bigelow. The 372 referred 
to reads as follows: 
‘The first effect of the motion in the upper 
strata of the atmosphere from the equator 
toward the pole, as in the case of the water 
flowing from the warmer toward the colder end 
of the canal, would be to fill up a little, as it 
were, the polar region with air from the equa- 
torial, the effect of which is to increase the 
pressure a little in the former and to decrease 
it a little in the latter region, thus creating at 
the earth’s surface and in the lower strata a 
gradient of pressure decreasing from the pole 
toward the equator, which would cause a 
counter current in the lower strata.’’ 
Ferrel does not state here whether the counter 
current would be anticyclonic or not, but states 
in other passages that such a gradient under 
the influence of the earth’s rotation would pro- 
duce an anticyclonic circulation. However, 
we are not left to inference in regard to Ferrel’s 
views in this matter, for in the American Jour- 
nal of Science (2 Ser., XXXI., p. 33, par. 15) he 
states his views explicitly as follows: 
“‘ Near the poles the tendency to flow toward 
the equator seems to be the greater, and causes 
a current there from the poles, which being de- 
flected westward (5) causes a slight northeast 
wind in the north frigid zone, and a southeast 
wind in the south frigid zone. But this is only 
near the earth’s surface, and the general tend- 
ency of the atmosphere in the upper regions 
must be toward the east as will be seen.”’ 
In the paper just quoted Ferrel gives a dia- 
gram of the air circulation in the polar cold-air 
cyclones which shows the circulation about the 
north pole as given in Fig. 4, in which I have 
made the north pole the center of the circula- 
tion for comparison with the eclipse circula- 
tion. The circulation around the pole indi- 
cated by Ferrel agrees with that shown by ob- 
SCIENCE. 
[N. S. Vou. XIII. No. 332. 
servations, as will be seen by comparing it 
with the carefully prepared charts in the 
‘Report on the Scientific Results of the Explor- 
ing Voyage of H. M. §. Challenger, 1873-76’ 
(Vol. II.). 
The similarity to the wind circulation found 
in the eclipse area must be apparent to every 
one (compare Figs. 3 and 4). The chief differ- 
ence is that the anticyclonic circulation around 
the center, as compared with the surface inflow, 
is relatively larger in the eclipse circulation, 
and the outer circle of outblowing winds in the 
latter is only faintly indicated, owing to lack of 
observations. But the larger anticyclonic cir- 
culation around the center in the eclipse is 
exactly what theory would indicate for a circu- 
lation over a continental area where surface 
friction is great, and in a case where the 
gradient necessary to overcome the friction is 
feeble. 
It may be asked why the diagram quoted 
here from Ferrel differs so radically from those 
given by Professor Bigelow. The explanation, 
I think, issimple. Ferrel, for the purpose of 
mathematical treatment, in the examples which 
Professor Bigelow quotes, was dealing with 
ideal cases in which there was little or no fric- 
tion When his theory was applied to actual 
conditions on a globe possessing friction, his 
illustration of the cyclone with a cold center 
was like that I have given, with an increase ‘of 
pressure and an anticyclonic circulation in the 
center at the earth’s surface. The greater the 
friction the larger the central anticyclone must 
be to overcome the friction and maintain the 
circulation. 
This view of Ferrel’s theory is exactly that 
taken by Professor Davis, who is probably the 
ablest student of Ferrel in this country (Quar. 
Jour. of the Roy. Meteor. Soc., April, 1899, p. 
165). 
The necessity of making every detail clear 
about the eclipse cyclone makes it necessary to 
omit consideration of the diurnal cyclones, but 
I think enough has been said to make clear the 
reasons for the contrasted views of myself and 
Professor Bigelow. 
H. HELM CLAYTON. 
BLUE HILL OBSERVATORY, 
April 16, 1901. 
