Dec, 15, 1881] 
NATURE 
Or 
SG 
of the south-west winds by the South Downs of Dorset- 
shire, and also, though in a less degree, from the east 
winds by the Isle of Wight. 
Since the averages here used are all for the twenty-four 
years ending with 1880 for the temperature, and for the 
twenty-one years ending with 1880 for the rainfall, the 
figures for these two chief elements of climate are strictly 
comparable throughout. The result is that all strong 
statements sometimes made in favour of local climato- 
logies, such as the rainfall of Ventnor being as small as 
that of London, entirely disappear. Such differences 
could easily be found by the results of different terms of 
years suited to the purpose, being selected for the par- 
ticular places whose climatologies are compared. All 
such comparisons, however, are not merely worthless, 
they are misleading. 
It is, however, now indubitably shown that the south 
coast of England, from Dover to Portland, enjoys the 
best winter climate anywhere to be found in the British 
Islands as respects the two important qualities of mild- 
ness and dryness combined, and it is highly probable that 
the climate of the same tract has clearer, brighter skies, 
and consequently more sunshine, than elsewhere in these 
islands. In view of the results of Buchan and Mitchell's 
investigation into the weather and health of London 
(NATURE, vol. xxiv. pp. 143 and 173) it is evident that 
it is to the South of England the invalid who suffers 
from bronchitis, pneumonia, or other throat diseases, 
must look for the climate best suited in the treatment of 
his case, and that it is to the same climate, owing to its 
clearer air, brighter skies, and more frequent sunshine, 
that those suffering from nervous and mental diseases 
should look as more likely to give them the relief they are 
in search of, 
TORNADOES, WHIRLWINDS, WATERSPOUTS, 
AND HAILSTORMS 
I. 
HILE identical with and resembling cyclones in not 
a few of their leading characteristics, tornadoes 
and whirlwinds are yet in several all-important respects 
widely and radically different. The largest tornadoes 
are of so small dimensions when compared with the 
smallest cyclones as to point to a difference so decided 
that admits of no shading of the one class of phenomena 
into the other. Again, cyclones occur at all hours of the day, 
whereas whirlwinds and tornadoes are all but restricted 
to the warmer hours of the day, and perhaps altogether 
to the time of the day when the sun is above the horizon. 
Further, and intimately connected with the above, cyclones 
take place under conditions which imply unequal densities 
at the same heights of the atmosphere, whether these be 
due to inequalities in the geographical distribution of 
temperature or humidity ; but whirlwinds occur where 
the air is unusually warm or moist for the time, and where, 
consequently, temperature and humidity diminish with 
height at an abnormally rapid rate. To put it otherwise, 
cyclones are phenomena consequent on a disturbance of 
the equilibrium of the atmosphere considered horizontally, 
but tornadoes, on the other hand, have their origin in a 
vertical disturbance of atmospheric equilibrium. 
Hence whirlwinds are of occasional occurrence nearly 
everywhere, penetrating into regions where cyclones are 
altogether unknown ; and even tornadoes, which are the 
most violent and destructive manifestations of the whirl- 
wind, are phenomena either of rare or of frequent occur- 
rence in nearly ail climates. 
Among the most remarkable of the tornado-swept tracts 
of the globe are certain portions of the United States of 
America ; and to the examination of these the Meteoro- 
logical Service of the States has given special attention 
by a systematic, careful, and minute observation of their 
attendant phenomena and their destructive effects. The 
results of these inquiries have been for some years re- 
corded with great, but by no means too great, fulness and 
elaborateness in the annual meteorological reports of the 
Chief Signal Officer. Much has been done of late years, 
as our readers are aware, by observation and discussions 
of observations, to throw light on these atmospheric 
meteors; and in this connection we have the greatest 
pleasure in referring to Prof. Ferrel’s recently published 
“Cyclones, Tornadoes, and Waterspouts,’’ Part II., the 
portion of which, bearing on tornadoes and whirlwinds, is 
the most successfully handled part of that very suggestive 
work, and indeed presents the best theory of whirlwinds 
yet propounded. 
Tornadoes, whirlwinds, and waterspouts are essentially 
the same, differing from each other only in their dimen- 
sions, their intensity, or in the degree in which the 
moisture is condensed into visible vapour; while the 
extraordinary downfalls of hail or rain, constituting the 
hailstorm and rainstorm, are simply the manner and 
degree of the precipitation. In the waterspout the main 
features of whirlwinds are best seen, owing to the degree, 
more or less complete, in which the vapour has been 
condensed into visible cloud through the whole length of 
the meteor. 
Figs. 1, 2, and 3 represent different forms of the water- 
spout. In Fig. 1 is seen the black cloud covering the 
sky, from which a projection is let down from the cloud 
in the form of an inverted cone as at A, which continues 
to increase and extend downwards, The surface of the 
sea at D immediately beneath is soon seen to be stirred, 
and quickly thrown into a state of violent agitation. At 
this stage the whirling movement which originated in the 
clouds has extended downwards to the sea, and is doubt- 
less continuous throughout, though the portion of the 
whirling column from A downward is not yet present to 
the eye by the condensation into cloud of its contained 
moisture. The come at A continues to lengthen down- 
wards, and ultimately reaches to the earth’s surface as 
shown at B and C, and by the waterspouts of Figs. 2 and 3. 
As the whirling movements of the aérial column of the 
waterspout become more intensely developed, the in- 
creasing rapidity of the gyrations brings about increased 
rarefaction of the air within, with the inevitable result of 
increased condensation into cloud downward. The pro- 
trusion from the clouds and extension toward the surface 
of the sea of the waterspout is thus not due to the descent 
of vapour from the clouds, but to the visible condensation 
of the vapour of the spirally ascending air-currents arising 
from an increasing rarefaction due to the accelerated rate 
of the gyrations, the condensation being similar to that 
of the cloud seen in exhausting an air-pump. 
The onward progressive motion of tornadoes and whirl- 
winds varies greatly, and is probably in all cases that of 
the general movement of that portion of the earth’s atmo- 
sphere in which they are embedded and form a part. 
Tornadoes sometimes rage with destructive violence on 
heights and hill tops, while intervening valleys remain 
untouched, thus showing that they occasionally occur at 
comparatively small elevations, but do not reach down to 
the surface of the earth. It also sometimes happens that 
the tornado in its onward course rises for a brief interval 
above the surface and again descends. As soon as the 
rapidity of the gyrations of the column become diminished, 
the rarefaction of the air of the column and the conden- 
sation of the vapour are correspondingly lessened, and 
thereafter the waterspout gradually breaks up and dis- 
appears. 
Under each of the waterspouts in Figs. 1, 2, and 3 the 
surface of the sea is seen to be more or less heaped up as 
well as in violent commotion, indicating that atinospheric 
pressure immediately under the gyrating column is less 
than it is all round. On land, when a tornado passes 
directly over a closed building, many instances have 
occurred_when the whole building, .walls and roof, has 
