68 
Cyclones were amongst the greatest wind storms which occur. 
They were mostly of acircular form, and varied in size from fifty miles 
in diameter to several hundred. Buijs Ballot, the Dutch meteorologist, 
says :—“It is a fact above all doubt, that the wind that comes is nearly 
at right angles to the line between the places of highest and lowest 
barometer readings. The wind has the place of lowest barometer at 
its left hand and is stronger in proportion as the difference of barometer 
readings is greater.” This applied to the northern hemisphere, the 
reverse occurring in the southern. This law was important, as it 
enabled us clearly to understand the modern cyclonic theory. If 
there was a region of low atmospheric pressure in the northern 
hemisphere, by drawing lines from the centre of the circle, where the 
pressure was lowest, to the circumference, where it was higher, then 
we found the wind came at right angles to each of these lines, having 
the centre of depression on its left hand ; the winds would thus blow 
round the depression against the sun or in the reverse direction to that 
of a watch’s hands. Another way in which the same law was stated was 
“that with your face to the wind the centre of depression is on the 
right hand.” Of course the law was reversed in the southern hemi- 
sphere. 
According to Buijs Ballot’s law, if there was a region of high 
pressure in the northern hemisphere, and the lines were drawn as 
before-mentioned, from the centre of high pressure to the places of 
lower pressure around, the winds would then come at right angles to - 
these lines, with the low pressure outside and on the left hand: the 
winds would thus blow round with the sun or with the hands of a watch. 
To this phenomenon Mr. Galton gave the name of “ Anti-cyclone,” on 
account of its being the exact reverse of a cyclone. Inthe centre of a 
large cyclone there was generally a calm. It was considered by many, 
and probably very correctly, that all the winds which prevailed in 
Europe were cyclonic in character ; a careful investigation of the daily 
weather maps for two or three weeks would show that several cyclones 
and anti-cyclones had passed over this country. Recently, however, a 
serious question had been raised as to the form of cyclones. Mr. Mel- 
drum, Director of the Government Observatory, Mauritius, stated that, 
as the result of several years’ observation, the cyclones in the Indian 
Ocean were not circular, but elliptical, and that the wind blowing from 
points from N.E. to S.E., blew almost directly towards the centre. 
‘Now, according to the previous rule, with the wind blowing from S.E, 
~~ 
Cte ie 
“a 
Phe me. 
