FLORIDA STATE HORTICULTURAL SOCIETY 
167 
to freeze makes Florida less liable and 
vice versa. 
Let us emphasize the fact pointed out 
by Prof. Brooks that winters with the 
maximum number of sun spots are not 
only somewhat colder in average temper¬ 
atures but are frequently winters with un¬ 
even temperature, with great extremes of 
heat and cold, warm periods alternating 
with cold periods. It is this kind of a 
winter of course, that does the damage, 
not so much the degree of cold as the al¬ 
ternating of cold periods with warm 
periods. Temperatures during such win¬ 
ters are more variable. We might call 
them variable winters. 
Sun spots have a tendency to occur in 
cycles from 9 to 13 years with an average 
of 11 years. Furthermore, there is a 
greater cycle from 80 to 100 years. There 
are many periods of sun spot areas which 
have not brought freezes in Florida. 
Some of the very highest sun spot max¬ 
ima have not brought freezes. On the 
other hand, with one or two exceptions, 
all the freezes we have had have occurred 
during such periods of maximum sun 
spots, and with only one or two excep¬ 
tions the period of low sun spot activity 
have been periods without severe freezes 
in Florida. There is apparently a strong 
correlation between freezes and sun spot 
maxima. It would seem that the correla¬ 
tion is altogether too close to be due to 
accident. There must be a relation of 
cause and effect between the two, or per¬ 
haps both freezes and sun spots are due 
to the same common cause. 
It is not our purpose to predict freezes 
for Florida but rather to indicate the 
periods of danger which are recurring on 
an average of about every n years, or 
perhaps to put it better, to call attention 
to the fact that there are periods of six 
or seven years’ duration occurring every 
11 years on an average which would 
seem to be pretty safe. Although this 
would seem more or less speculative, it 
would seem that the correlation is close 
enough to be of some value to Florida 
growers, as fore-warned should be fore¬ 
armed, to some extent, particularly as sun 
spots can be observed throughout the year 
and it would be possible to give warning 
as to these dangerous periods. For in¬ 
stance, the Weather Bureau has pointed 
out that the unusual weather which dom¬ 
inated the winter of 1917 began early in 
August; that is to say, the winter type of 
cyclones and anti-cyclones began to enter 
the country from the northwest as early 
as the first week in August, which is 
months earlier than usual. 
Perhaps the only conclusion we are 
justified in drawing from this is that 
there are certain periods which can rough¬ 
ly be predicted during which one may feel 
reasonably safe from freezes in Florida. 
We are now in such a period, and there 
are periods during which the reverse is 
true, and the grower should perhaps take 
particular pains to apply the usual precau¬ 
tions against cold weather during these 
periods. The next period of maximum 
sun spot activity would be expected to cul¬ 
minate about 1929, 11 years after 1918, 
the last maximum. 
Brooks has shown that during these 
periods of maximum sun spots that the 
Gulf Stream is warmer than usual but 
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