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Hall, Maxwell

The meteorology of Jamaica

INSTITUTE OP JAMAICA

THE

METEOEOLOGY OF JAMAICA

KINGSTON, JAMAICA:

The Institute of Jamaica : Date Tree Hall.

Agents in London : H, Sotheran & Co., 140 Strand & 37 Piccadilly, "W".

Agents in New York : G. P. Putnam's Sons, 27 & 29 West 23rd Street.

1904.

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THE

METEOEOLOGY OF JAMAICA

BY

MAXWELL HALL, M.A, F.R.A.S., F.E.Met.S.,

MEM. HOX. SOC. IXNEPw TEMPLE.

KINGSTON, JAMAICA:

The Institute of Jamaica: Date Tree Hall.
Agents in London : H. Sotheran & Co., 140 Strand & 37 Piccadilly, W.
Agents in Xew York : G. P. Putnam's Sons, 27 & 29 West 23rd Street.

1904.

ad ^

H3

PRINTED BY
WILLIAM CLOWES AXD SONS, LIJIITED,
LONDON" AND BECCLES.

PREFACE

In ancient times Meteorology included all the appearances of
the heavens, whether astronomical or atmospheric. But as
knowledge increased, these appearances, or phenomena, were
gradually referred to either one or the other of the two
divisions.

Astronomy became an exact science — that is to say, all
the observed motions were found to be subject to strict laws
and rigorous computation ; but the laws which regulate the
ever-varying atmospheric motions and changes are so highly
complicated, that, even at the present time, Meteorology can
hardly be termed a science.

But in an uniform climate like that of Jamaica the
diurnal and annual variations are so far regular that obser-
vation alone affords highly valuable and practical results ;
and it is here proposed to give an account of some of the
more important results of observation as detailed in the
Jamaica Weather Reports, which were issued monthly between
1881 and 1902, and which form Vols. I., 11. , and III. of the
Jamaica Meteorological Observations.

It is also proposed to give a few simple explanations
of the changes which are found to occur, with the view of
rendering such knowledge as we possess practically useful,
and with the hope of aiding future research.

A few remarks will be made about the instruments

4 PREFACE

employed in measuring the pressure, temperature, motion,

and moisture of the atmosphere, and their management ;

and this part of the work is merely a revision of the article

on Meteorology published in the first Handbook of Jamaica,

1881.

MAXWELL HALL.

MoNTEGo Bay,

February, 1904.

CONTENTS

The Barometee

PAGE

7

The Thermometek

11

Vapour

15

Ratn

19

The Winds

22

Clouds and Cloud-drifi'

25

Cyclones

31

Tables

36

THE

METEOEOLOGY OF JAMAICA

The Barometer

This instrument Tvas invented by Torricelli in the year
1643, and its principle may be illustrated by the following
experiment.

Take a glass tube about three feet in length, closed at one
end, and fill it with mercur3^ Now close the open end by
pressure of the finger, invert the tube, dip the end closed
by the finger into a bowl containing mercury, and then
remove the finger. It will be found that the mercury will
fall a few inches in the tube, leaving a vacuum at the upper
end ; and upon measurement it will be found that the height
of the column of mercury in the tube above the surface of the
mercury in the bowl will be about 30 inches, provided that
the experiment be made near the level of the sea.

Torricelli thus demonstrated that the pressure of the
atmosphere on any area near the sea-level is counter-
balanced by the pressure of a column of mercury on that
area whose height is about 30 inches.

In the barometer the bowl is replaced by a small glass
cistern ; the cistern and the glass tube are enclosed in a
suitable brass frame ; and arrangements are made for
measuring with great accuracy the height of the column
of mercury above the level of the mercury in the cistern.
This is what is to be understood by "the height of the
barometer."

The brass framework has a thermometer attached to it,

8 THE METEOROLOGY OF JAMAICA

in order to show the temperature of the instrument — for the
following reason.

The density of mercury varies with its temperature, so
that a column of 30 inches of mercury at a temperature of
50° weighs more than a column of 30 inches of mercury at
80°. In order, therefore, to compare the readings of baro-
meters at different temperatures, it is necessary to reduce
all these readings to what they would have been, supposing
that the mercury had always the same temperature.

It has been universally agreed to adopt 32°, the tempera-
ture of freezing water, as the temperature of reference for
mercurial barometers.

Table I. gives the decimal parts of an inch to be subtracted
from the reading of the barometer for every degree between
60° and 90° ; it takes into account the expansion of the brass
frame as well as the expansion of the mercury. It will
be seen that the reduction varies with the height of the
barometer; thus when the attached thermometer is 75° we
must subtract 0"108 inch from the reading of the barometer
when it is about 26 inches, but we must subtract 0'125 inch
when the reading is about 30 inches.

Now, although Torricelli showed that the atmosphere
exerted a pressure which could be measured by a barometer,
it was left to Pascal to show that this pressure was due to
the weight of the air. The atmosphere rests upon the
surface of the sea and land in much the same way that
the ocean rests upon its bed. The pressure at great depths
in the ocean is enormous ; the atmospheric pressure at the
surface of the sea is about 15 pounds on every square inch ;
and this pressure continually diminishes as the elevation
above the level of the sea increases.

In the year 1648, at the suggestion of Pascal, Perier
ascended the Puy de Dome, a mountain near the centre
of France ; and he found that the barometer fell almost
four inches as he ascended from the foot of the mountain
to its summit. The pressure at the summit was relieved
of the weight of the air below ; and it only remained to
ascertain the weight of a given quantity of air in order to
compute differences of elevation by means of barometric
observations.

THE BAROMETER 9

This can be done with considerable accuracy ; and con-
Tersely, when a barometer is read at a given elevation, the
reading can be reduced to the level of the sea.

Table 11. gives the reduction of the barometer to the sea-
level for different temperatures of the air at the sea-level.
When the temperature of the air at any given elevation is
known, the temperature of the air at the sea-level can be
obtained approximately from Table YI. ; thus, at the Blue
Mountain Peak, which is 7423 feet above the level of the
sea, the temperature falls on an average 23°"5 below the
temperature at the level of the sea ; and at this elevation
it makes little difference in the fall of temperature whether
we consider the fall at the hottest or the coolest time of the
twenty-four hours ; but at other elevations the difference may
be sensible, and should be allowed for if necessary.

The next correction to be applied to the barometer is
for all the instrumental errors combined, including any very
slight difference in the specific gravity of the mercury em-
ployed, and that of the mercury in the standard of the Koyal
Society. All barometers intended for accurate purposes are
therefore sent to the Kew Observatory to be compared with
the standard ; the differences are carefully noted, and may
be termed the reductions to the Kew standard. This reduc-
tion for a well-made instrument will never exceed a few
thousandths of an inch.

Finally, a small correction depending on the latitude
should be applied in consequence of the variation of gravity
with the latitude. Terrestrial gravity is greatest at the
X)oles and least at the equator ; so that a column of mercury
30 inches high at the equator would balance a column of
mercury of only 29*84 inches at the poles, the two columns
having the same temperature. Consequently, in comparing
barometric pressures in different latitudes, it becomes necessary
to adopt some standard gravity; and it has been agreed to
adopt gravity at the sea-level in lat. 45" as such standard.

Different nations have recently adopted this correction at
different times ; and I believe that it was agreed that all
nations who had not previously done so should adopt it
on January 1, 1901. In Jamaica the correction was adopted
January 1, 1896; and 0*063 inch, corresponding to lat. 18^

A 2

lo THE METEOROLOGY OF JAMAICA

was subtracted from all barometric readings reduced to the
sea-level.

This reduction to standard gravity should be incorporated
with the reduction to the Kew standard ; and for any altitude
not exceeding a thousand feet or so, a small table should be
drawn up further reducing to 32° and to sea-level for each
degree of temperature as usually experienced at the station
in question, always supposing that the barometer is kept
where its temperature as shown by the attached ther-
mometer will not greatly differ from the temperature of
the air as shown by the dry-bulb thermometer in Stevenson's
screen on the lawn.

Commencing observations, the first thing which attracts
our attention is the diurnal variation of the atmospheric
pressure ; two small waves pass daily with great regularity,
the crests at 9.30 a.m. and 10.30 p.m., and the hollows at
4 p.m. and 3.30 a.m. The wave which passes during the
daytime is about twice as great as the one which passes
during the night ; and neither of them is affected by heavy
local rains, nor yet by cyclones, however widely extended.

Table III. gives the correction for this diurnal variation
to be applied to the reduced reading of the barometer ; and
it cannot be neglected when accuracy is required. Thus,
suppose about the middle of August that the reduced reading
at 7 a.m. was 29*910, and at 3 p.m. 29*869 : by neglecting
the diurnal variation it would appear that the pressure was
falling ; but by applying the correction it will be found that
the pressure was really steady, the corrected reading being
29*900 both at 7 a.m. and 3 p.m.

Now, the mean pressure of a day at any place is the sum
of the twenty-four reduced readings of the barometer taken
at each hour of the day and night divided by 24 ; the
mean pressure of a month is the sum of the daily means
divided by the number of days in the month ; the mean
pressure of a year is the sum of the monthly means divided
by 12 ; and the mean pressure at the place is the sum
of the annual means divided by the number of years of
observation.

Table IV. gives the mean pressure at Kingston sea-level
for every ten days throughout the year ; and by its use we

THE THERMOMETER ii

can ascertain whether the mean pressure of any clay is above
or below the average.

The mean pressure of a day is, of course, independent
of the diurnal variation ; and it will be noticed in Table III.
that if we take the mean of the three reduced readings at
7 a.m., 3 p.m., and 11 p.m., we shall get a very close approxi-
mation to the mean pressure of the day as deduced from the
twenty-four hourly readings.

The best hours for observation of pressure are therefore
7 a.m., 3 p.m., and 11 p.m., especially as it will be found in
the next section that the 7 a.m. and 3 p.m. readings of the
thermometer are the best hours for the observation of
temperature.

The Thermometer

was invented by Galileo towards the end of the sixteenth
century. His air thermometer consists of a glass bulb with
a long neck, which is dipped into a small cistern or vessel
containing coloured liquid. As the air in the bulb expands
or contracts according as its temperature increases or
diminishes, so the coloured liquid ialls or rises in the neck,
to which a scale is attached to mark the variations. But in
order that the coloured liquid may have a convenient normal
height in the neck, it is, of course, necessary to heat the
bulb before the neck is plunged into the liquid.

Such an instrument as this will show variations of
temperature, provided that the atmospheric pressure remains
the same ; if the atmospheric pressure increases or diminishes,
the elastic glass bulb will contract or expand and vary the
height of the liquid.

The instrument was afterwards improved; the neck
became a thin stem ; the bulb was greatly reduced in size
and filled with spirits of wine or mercury ; and the glass
stem was hermetically sealed by means of the blow-pipe, so
as to exclude the air entirely. Variations of temperature
were now shown by the expansion or contraction of the fluid ;
and all that was required was a scale.

In the year 1701 Sir Isaac Newton pointed out that there
were two temperatures adapted for the purposes of graduation.

12 THE METEOROLOGY OF JAMAICA

These were the temperature of freezing water and the tempera-
ture of the human body ; and it was not till afterwards that
the latter temperature was replaced by that of boiling water.
If a thermometer be placed in a tumbler containing ice and
water, its temperature will remain steady until all the ice is
melted or all the water frozen ; if the thermometer be placed
in an open vessel of boiling water, its temperature will again
remain steady until all the water is boiled away. By in-
creasing the fire under the open vessel the temperature of
the water is not increased ; it only boils away faster. The
boiling-point, however, varies slightly with the pressure.*

Fahrenheit, a philosophical instrument maker of Amster-
dam, constructed his scale about the year 1724. He divided
the distance between the freezing- and boiling-points into 180
parts ; and he took as the zero a point 32 of these divisions
below the first ; so that on his scale 32° and 212° are the
freezing- and boiling-points respectively.

The centigrade division of the scale was introduced by
Celsius, a Swede, in the year 1712. The freezing-point was
taken as zero, and marked 0°; and the boiling-point was
marked 100°.

The latter scale is well adapted for the study of physics ;
the former is, however, more convenient for everyday require-
ments. When using Fahrenheit's scale we have seldom to
refer to negative temperatures, or temperatures below zero ;
and we have seldom to express temperatures in degrees and
tentlis ; but when scientific purposes require registration to
tenths of a degree, then Fahrenheit's scale again affords the
required accuracy.

Fahrenheit's scale is used in English-speaking countries ;
the Centigrade scale is used in France, Sweden, and other
countries ; and Reaumur's scale is used in Germany and
Eussia. In the last scale the freezing-point is 0° and the
boiling-point 80° ; it possesses no known advantages.

Very accurate and comparatively cheap thermometers
can now be procured with the divisions etched on their stems ;
but still it is necessary that all such thermometers should be
compared with a standard thermometer at intervals of a few
years in order to ascertain tbeir errors.

* It is 212° when the pressure is 29 938 (stand, grav.).

THE THERMOMETER 13

For meteorological purposes it is the temperature of the
air which is required. At night, or on a cloudy day, when
the air is moving, the temperature may be easily found ; but
when the day is calm, and the solar radiation intense, it is no
easy matter to obtain the temperature of the air. Uniformity
of exposure therefore becomes very important, so that we may
at least compare the temperature of different places.

Stevenson's screen for thermometers is now very generally
adopted. It is a light wooden box, whose sides are made of
double jalousie- work, so that the rays of heat from the sun or
ground cannot reach the thermometers, and so that the air
can freely circulate about them. The screen is supported by a
firm wooden stand; it is freely exposed to the air on a grass
lawn ; and its height is such that the bulbs of the thermometers
are 4 feet G inches above the surface of the ground.

There are two important modifications of the ordinary
thermometer which may be briefly alluded to ; the first is
adapted for the self-registration of the highest temperature
reached by the thermometer in any given interval of time.
In the ordinary thermometer a small piece of steel or enamel
is placed in the empt}- part of the tube ; this index is free to
move in the tube ; it is brought into contact with the mercury
during the cooler part of the day, and the tube is placed in a
horizontal position. As the mercury expands the index is
pushed forward to the highest point, and is left remaining
there after the mercury contracts. This modification is
called the maximum thermometer, and it is registered once
in every twenty-four hours, so as to obtain the highest
temperature of the day. There are, however, several forms
of this instrument.

The other modification is called the minimum thermometer,
as it registers the lowest temperature of the day. In this
instrument alcohol is used instead of mercury, and the index
is placed in the alcohol in the tube ; as the alcohol contracts
it drags the index down to the lowest point, and as it expands
it passes by the index, leaving it stationary at the lowest
point. The difference between the highest and lowest
temperatures of any day is called the Eange.

Now, the mean temperature of any day may be found with
considerable accuracy by merely subtracting V from half the

14 THE METEOROLOGY OF JAMAICA

som of the maximum and minimum temperatures of the day ;
or by taking half the sum of the temperatures at 7 a.m. and
3 p.m. And by combining these two precepts we get the fol-
lowing rule for mean temperature in Jamaica : add together
the 7 a.m., 3 p.m., maximum, and minimum temperatures,
subtract 2° from their sum, and divide the remainder by 4.

By employing monthly means we similarly get the mean
temperature of the month.

Table V. gives the results for Kingston, about 50 feet
above the sea-level, as deduced from careful observations
made by the Weather Service between the years 1881 and
1898 inclusive ; and it will be seen that the mean temperature
of Kingston is 78°-8.

Now from similar observations made at the Cinchona
Plantation (or Hill Gardens), elevation 4907 feet, by the
Department of Public Gardens and Plantations, it appears
that the mean temperature there is 62°*2 ; and from some-
what different observations made on the ]>lue Mountain Peak
by the same Department, it appears that the mean tempera-
ture of the Peak is 56°'0 at an elevation of 7423 feet. The
mean temperature therefore falls about 1° for every 300 feet
of elevation ; more accurately, the mean temperature falls
3°*4 for the fall of an inch of barometric pressure.

But the fall of mean maximum and minimum temperatures
is more complicated, and Table YI. has been drawn up in a
form convenient for general use.

With regard to extreme temperatures, at Kingston the
highest maximum was 96°'7, recorded on August 20, 1891,
and the lowest minimum was 56' '7, recorded December 4,
1887 ; at the Peak the highest maximum was 80'^'9, recorded
in February, 1889, and the lowest minimum was 33°"3,
recorded in February, 1893.

From observations in Kingston extending over two years,
it appears that the minimum temperature on the grass is 6°
below the minimum temperature inside the Stevenson screen
4J feet above the lawn. Now the temperature in the screen
at the Peak fell to 38°, or below 38°, twelve times during the
sixteen years of observation ; consequently frost occurred on
the Peak twelve times during those sixteen years.

The diurnal variation of the temperature is, of course, well

VAPOUR 15

■understood ; the minimum occurs at sunrise ; the temperature
then rises rapidl}', the maximum occurring at noon. In the
evening the temperature falls until the dew-point is reached,
when the rate of fall is arrested, and then the temperature
•slowly decreases to the minimum at sunrise.

Table VII. gives the diurnal variation for Kingston in the
form of a correction to be applied to the temperature at any
hour to reduce it to the mean of the twenty-four hours. It
was deduced from hourly observations made during the years
1899, 1900, and 1901, at the United States Station, Halfway
Tree, by means of a self-recording instrument.

Vapour

Air consists of two gases, oxygen and nitrogen, which are
mixed together in the proportion of 23 parts of oxygen to
77 parts of nitrogen, with respect to weight.

But the atmosphere also contains a little carbonic acid
gas, and a variable quantity of the vapour of water. The
amount of this aqueous vapour is measured by its pressure,
or tcusioiif as it is termed, in the same manner that the whole
pressure of the atmosphere is measured. Thus, while the
atmosphere at the sea-level exerts a pressure of about 30
inches of mercury, the amount of vapour generally present in
the atmosphere exerts a tension of about a quarter of an inch
in cool climates, and in warm insular climates about three
times as much.

Now, while aqueous vapour resembles a true gas in most
respects, such as elasticity, invisibility, etc., yet it differs in
this important particular, that a given volume cannot contain
more than a certain amount of vapour depending on its
temperature.

If a little water be poured into a glass jar, which is then
tightly closed, the jar will soon become filled with a certain
definite amount of vapour depending on the temperature, but
independent of the air which may be in the jar ; that is to
say, the amount of vapour will be the same whether the jar
was full of air or whether it had been previously exhausted.

By increasing the temperature within the jar, the amount
of vapour will be increased ; by diminishing the temperature,

16 THE METEOROLOGY OF JAMAICA

the amount will be decreased, the vapour will be condensed,.
and form minute drops of w^ater, which adhere to the
sides of the jar, or trickle down to join the water at the
bottom.

In this way dew is formed. At night the temperature of
the grass, leaves of trees, roofs of houses, etc., is reduced by
radiation ; the air near them is chilled, and it cannot then
contain all the vapour it previously sustained ; the excess is
quietly and gradually deposited in the form of dew. In the
country the amount of dew is so large that it drips from the
eaves of the houses like rain. In Kingston the air is much
drier, and there is but little dew.

In this way, again, clouds are formed and rain produced.
But we have said enough to show the importance of aqueous
vapour, and we must now return to its measurement.

If from an elaborate series of experiments, we knew the
tension of saturated vapour for each degree of temperature, we
could ascertain the amount of vapour present in the air at
any given time and place by noting the temperature of the
dew-2)oint, or the temperature at which dew begins to form.

Such experiments have often been made, but the best
were conducted by Eegnault, the French chemist ; the results
are given in the second column in Table VIII.

In order, therefore, to find the amount of vapour present
in the air at any time, it is only necessary to find the dew-
point and to employ Table VIII. Thus, if the average tem-
perature of the dew-point is 70^*3 in Kingston, the aqueous
vapour in the air there exerts an average pressure or tension
of 0*741 inch.

But in order to find the dew-point, it is generally necessary
to reduce the temperature. This may be done by ether; and
Daniel's hygrometer is adapted to thedirect observation of the
dew-point.

Such observations, however, would be tedious, and the
dry- and wet-bulb hygrometer is used in preference. If the
bulb of a thermometer be wrapped in some very thin muslin
and kept continually damp by means of a connecting thread
which dips into a small cistern of water, the thermometer
will show the temperature of evaporation, which depends on
the rate of evaporation, which again depends on the amount

VAPOUR 17

of vapour there is in the air, and the amount of wind moving.
By placing dry- and wet-bulb thermometers side by side in
a Stevenson screen, the effect of the wind will be greatly
reduced, and may then be neglected. And so we have left
for consideration the difference of the readings of the dry- and
wet-bulb thermometers and the amount of vapour.

Now, from a long series of experiments, it has been found
that if the difference between the dry- and wet-bulb read-
ings be multiplied by certain factors, or numbers, we shall
obtain the difference between the temperature of the dry bulb
and the temperature of the dew-point, which thus becomes
known. Glaisher's experiments include observations made in
different climates, and during balloon ascents. By means of
Daniel's hygrometer, it has been found that they are equally
applicable to the hot plains in Jamaica and to the Blue
Mountain Peak. Glaisher's factors are given in the third
column in Table VIII.

In practice, however, it will be convenient to subtract
unity from these factors ; and then after multiplying the
difference between the dry and wet bulbs by the diminished
factor, we get the difference between the wet bulb and the
dew-point. As an example, suppose that the readings of the
dry and wet bulbs are 85^ and 75° respectively ; we must
multiply their difference 10° by 1*65, the factor corresponding
to 85° ; this gives us 16°*5, the difference between the dry
bulb and the dew-point ; hence the dew-point is 68°*5. Or,
by diminishing the factor by unity, we must multiply 10° by
0'65, and subtract the product from 75°, which gives the dew-
point as before.

In this way tables can be prepared which give the dew-
point by mere inspection. Table IX. will be found generally
useful in Jamaica.

The diurnal variation of the dew-point in Kingston is
small —

7am fi9^*1

O U » UJ, • ••• ••• ,,, ••• ,,, ••« 4-j\/

XX U • IXJ • ••■ ••# •«• ••• ••• •■• \JU tj

giving an average, as already stated, of about 70°"3.

The annual variation of the dew-point is fairly large, and
closely follows the minimum temperature ; this is show^ in

A 3

i8 THE METEOROLOGY OF JAMAICA

Table XI. The explanation of this fact is very simple ; the
temperature falls at night until the dew-point is reached;
then dew is deposited, latent heat is given out, and the further
fall of temperature is arrested.

Above the sea-level the tension of the aqueous vapour
present might be expected to decrease with the atmospheric
pressure ; but the dew-point at the Cinchona Plantation is
only 58°,* giving a tension of only 0*482 inch ; and this
shows that we have to consider distance from the seashore
as well as elevation.

But besides the amount of vapour, we require to know the
humidity of the air. Thus in the example given above the
dry and wet bulbs were 85° and 75°, the dew-point was 68°*5,
and the tension of vapour was 0*696 inch. On another day
the dry and wet bulbs may both read 68°'5, and the tension
of vapour will be the same as before ; but the humidity is
different. On the first day the air was dry, and on the
second day the air was saturated with moisture.

Humidity may be defined as the ratio of the vapour-
tension present at any time to the vapour-tension required
for saturation ; and humidity is recorded in whole numbers
from 0, when the air is perfectly dry, to 100, when the air is
perfectly saturated.

Thus on the first day the temperature of the air was 85°,
and a tension of 1"203 inch was required for saturation. But
the tension really was 0*696 inch ; hence the humidity was
58 — which is found by multiplying 0*696 by 100 and by
dividing by 1*203. On the second day the humidity was, of
course, 100.

Table X. gives the humidity by mere inspection. This
and the two preceding tables were taken from Glaisher's
Hygrometrical Tables, which have, of course, a far larger scope,
and to which further reference may be made if necessary.

The diurnal variation of humidity in Kingston is fairly
large —

7 ;\.iii. ... ... ... ••• ••• ••• ••• ol

3 p.m. ... ... ... ... ... ... ... 68

11 p.m. ... ... ... ... ••• ... ... 85

* This is the mean of the 7 a.m. and 3 p m. readings, 55°-5 and 60°'5 respec-
tively; the ojrrespondiDg dew-point at Kingston is 70°-6.

RAIN 19

giving an average of about 78. These results apply to the
air 4 feet 6 inches above the ground ; nearer the ground the
humidity increases at night up to 100.

At the Cinchona Plantation the humidity at 7 a.m. is
about 83, which is much the same as at Kingston ; but at
3 p.m. it increases to 88 — probably due to afternoon showers,
which fall there nearly all the year round.

Rain

The amount of rain which falls at any place in any given
interval of time is measured by its depth in inches and
decimal parts of an inch.

Thus, let us suppose that at anj^ time the depth of water
in an open tank was 5 feet, and that after an interval of
twenty-four hours, during which there were intermittent
showers, the depth of water was increased to 5 feet 2 inches ;
then the total amount of rain which fell at the place during
those twenty-four hours was 2 inches in depth ; or, more
shortly, the rainfall for that day was 2 inches.

It is to be noticed that the size and form of the tank will
not affect the result, provided the sides of the tank are
perpendicular ; and, instead of a tank, we may use a small
cylindrical receiver, neatly made of thin metal.

Again, in order to measure with accuracy the depth of
the water caught at any time in the receiver, we can pour the
water into a narrow cylindrical glass gauge, properly graduated,
and thus easily read the rainfall to the nearest hundredth
part of an inch. In graduating these glass gauges the scale
must be multiplied by the ratio of the square of the diameter
of the receiver to the square of the diameter of the gauge.

Such an apparatus is called a rain-gauge ; and by register-
ing the rainfall daily we get the total rainfall for the month
or year. But on account of the extreme local irregularity in
the rainfall, it is necessary to read a large number of rain-
gauges in order to obtain the average rainfall for any district.
These rain-gauges should be placed so that the receiving
surfaces are all one foot above the surface of the ground ;
and, of course, they should be fully exposed to the sky, and

20 THE METEOROLOGY OF JAMAICA

in no way sheltered by trees or buildings. If the rain-gauges
cannot be placed so near the ground with safety, as is often
the case on sugar estates, they may be placed on the top of
a post 5 feet high, firmly planted in any open ground. The
height of the receiving surface above the ground, as well as
the elevation of the place above the level of the sea, should
always be stated in the register.

In Jamaica the hundredths of an inch are often called
"parts"; thus a rainfall of 2*03 inches, or two inches no
tenths and three hundredths, is often written 2 inches and
3 parts. It would often save confusion to adhere to the
proper decimal notation. When no rain falls 000 should
be entered in the register, and blanks should be left for
omissions to register.

The rain-gauge should be registered daily at 7 a.m.,
before the sun gets hot, otherwise there will be loss from
evaporation. But the rainfall should be entered in the
register for the preceding day, and not for the day on which
the entry was made. The necessity of this is obvious, as the
rains generally fall after noon.

There are about 200 rain-gauges registered in Jamaica,
but they are very irregularly distributed ; and in consequence
of this irregularity, the island was divided into four divisions.
Now if the average rainfall be obtained for each division, the
average rainfall for the whole island may be obtained by
adding together the average for each division and by dividing
by 4, no matter how many gauges may be registered in one
division and how many in another.

The northern division comprises the northern shores from
Port Maria to Davis' Cove, including the central part of the
island, which forms the central sub-division; the southern
division comprises the southern shores from Holland Bay to
South Negril ; the north-eastern and west-central divisions
are the remaining parts of the island, bounded by the sea and
the other divisions. Their relative areas are as follows : —

North-eastern division ... ... ... ... ... 25

Northern and central ... ... ... ... ... 22

West-central 2(>

Southern 27

100

RAIN 2r

The north-eastern and northern divisions have winter rains
in November, December, and January ; the north-eastern
and west-central divisions have summer rains ; and the
southern division is drier than the others, having rains for
the most part during the May and October " seasons " only;
and these characteristics of the Jamaica rainfall have not
altered for two hundred years at least.

Tables XII. and XIII. give us general information about
the rainfall; and it will be seen that the average annual
rainfall over the whole island is about 70 inches ; that in
1886 it rose to over 90 inches ; and that in 1872 it fell to 45
inches, in consequence of the failure of both the May and
October seasons. The heavy rainfall in 188G was chiefly due
to the flood-rains in June that year, which did immense
damage to property — the Pdo Cobre carried away railway
bridges and embankments ; the Eio Minho rose 40 feet above
its bed at the May Pen bridge ; and at the centre of the island
Cave Valley and Greenock estates were submerged in con-
sequence of the '' sink-holes" being choked, the water rising
in some parts as much as 100 feet.*

With regard to the distribution of the rainfall, Table XIII.
shows that far more rain falls in the north-eastern division
than in any other ; then follows the west-central division,
then the northern, and lastly the southern, as already stated.
But the rainfall varies greatly over each division. In the
north-eastern division the greatest rainfall occurs in the valley
of the Piio Grande at the base of the Blue Mountains. A rain-
gauge has been kept at Moore Town since February, 1896, and
it shows an annual rainfall of about 248 inches. At the
Blue Mountain Peak the annual rainfall is 175 inches ; and
at twelve other stations in the north-eastern division, where
registers have been kept for seven years and more, the annual
rainfall exceeds 100 inches.

In the west-central division there are only five stations
where the annual rainfall exceeds 100 inches.

Kingston, Plumb Point Lighthouse (two miles south of
Kingston), and Bull Bay (eight miles east of Kingston), are
the driest places in the island, their annual rainfall being 35,
34, and 33 inches respectively.

* For further particulars see Weather Eejport, Xo. 67.

22 THE METEOROLOGY OF JAMAICA

For further particulars reference should be made to the
Rainfall Atlas published by the Institute of Jamaica in the
year 1892, which shows the average rainfall over the island,
for the year, and for each month of the year ; and to Weather
Report, No. 256 (a), which gives the average rainfall at 193
stations where registers have been continuously kept for at
least six years.

The Winds

Wind is caused by local differences of atmospheric
23ressure, which, again, are chiefly caused by local differences
of temperature ; and its direction at any place and time is
indicated by the true point of the compass from which it
blows.

In Jamaica the difference between the true and magnetic
north is small ; at Kingston, in the year 1891, the magnetic
north was 2° 16' to the east of the true north ; and this differ-
ence decreases at present at the rate of about 7' per annum.

In order to show the prevailing direction of the wind at
any place for any month or year, it is convenient to construct
a table stating the number of times the wind was observed to
l)low from each point of the compass. In Kingston, for
instance, the prevailing direction of the sea-breeze is south-
east.

Besides the direction of the wind, we further require its
velocity, or force. The velocity of the wind is measured in
miles per hour. Dr. Eobinson of Armagh invented a very
useful anemometer. It consists of two light rods attached
together crosswise, which carry four light cups at their
extremities. These cups and rods are free to rotate horizon-
tally about a light vertical axis firmly attached to the rods at
their point of junction ; and by means of an endless screw
this vertical axis can be made to register the number of
revolutions of the apparatus. Dr. Eobinson showed that the
centres of the cups rotate with one-third of the velocity of the
wind ; and the registering dials are made to record three
times the number of miles passed over by the centre of the
cups in consequence of their rotation, or the number of miles
of wind which has swept past the instrument. If, therefore,

THE WINDS 23

we read the dials at the commencement and end of an hour
or day, we can obtain the number of miles of wind which
have passed the instrument in the hour or day. The former
is alluded to as velocit}' — so many miles per hour ; the latter
as the total miles of wind in the day. These anemometers
should be small and light ; for otherwise short and strong
gusts of wind produce a momentum so great that the cups
and rods do not cease to rotate when the gusts stop, and
consequently the readings are too large.

But besides the velocity, the force of the wind may be
measured by its pressure in pounds upon a square foot of
surface kept continually opposed to the wind by means of a
vane. There is, of course, an intimate connection between
the two — the pressure is equal to the square of the velocity
divided by 300. In Table XIV. it will be seen that while the
pressures are very small for small velocities, they increase
rapidly as the velocities increase, until velocities of 100, 110,
and 120 miles per hour produce pressures which sweep away
trees and buildings.

There is considerable doubt as to the accuracy of these
pressure-plate anemometers when the wind is violent ; the
clock-work recording apparatus is somewhat cumbersome,
and the recording pencil seems to be jerked forward so as to
indicate too high pressures. At the Kempshot observatory,
near Montego Bay, all the usual recording apparatus has been
removed from the pressure-plate anemometer, and a very light
needle moves an index forward, which remains at the highest
reading ; the instrument therefore registers the strongest
gusts onl}', and it registers them correctly as far as can be
ascertained.

Another anemometer was devised a few years ago by Mr.
Dines, on the principle that when the wind blows over the
mouth of a pipe the pressure of the air within the pipe
is diminished. It works ver}^ well ; and it would be interesting
to compare the indications of the three instruments when the
wind is over 60 miles an hour.

It must, however, often occur that instruments are not at
hand to measure the force or the velocity of the wind, and
consequently arbitrary scales are used. In Great Britain the
scale adopted was compiled especially for nautical purposes

24 THE METEOROLOGY OF JAMAICA

by Admiral Beaufort. But if we were to adopt this scale in
Jamaica, all our land-breezes would be put down as calms ;
and indeed it is evident that this scale is not sufficiently
refined for wind on shore with regard to the smaller velocities.
The scale used in the United States of America has been
adopted in Jamaica ; it is given in Table XV.

The explanation of the sea and land breezes is very
simple. During the daytime the land is heated by the sun,
while the sea hardly changes its temperature ; consequently
the air above the land rises and expands; the barometric
pressure is diminished; and the air from the sea flows in
from all directions to replace the ascending currents. During
the night the land is cooled by radiation, and the surface
currents of air move from the land outwards in all directions.
But these breezes in Jamaica are modified by the general
easterly drift of the air over the Caribbean Sea ; and the
results are strong north-east sea-breezes on the north side of
the island, and strong south-east sea-breezes on the south side.

The sea-breeze sets in about 10 a.m. and lasts until about
5 p.m. It is strongest at the level of the sea, and diminished
with the elevation ; so that at an elevation of 1000 feet it is
hardly felt.*

Table XVI. gives the diurnal variation of the wind at
Kingston from instruments placed on the roof of the Public
Works Office. The constancy from 9 p.m. through the night
to 8 a.m. is very remarkable, and there is no lull or calm at
all between the south-east sea-breeze and the north land-
breeze. Table XVII. gives the annual variation of the wind
at Kingston.

The prevailing easterly winds over Jamaica and the West
Indies generally are due to the great anticyclone which
exists over the North Atlantic, and the position of whose
centre is on an average in lat. 30°, long. 30° They are, of
course, part of the trade-wind system ; and to study them
we must get well above the sea-breeze limit. At both the
Kempshot observatory and at the Cinchona Plantation the
average direction is east ; but at the former place the
direction varies with the time of the year — east-north-east or
even north-east in winter, and east-south-east or even south-

* At Iver, St. Andrew, elevation 1700 or 1800 feet, it is distinctly felt.

CLOUDS AND CLOUD-DRIFT 2$

east in summer. This variation is in direct accordance with
the diminution of the anticyclone in winter, and the low
IDressure over the North American continent in summer ; and
it is difficult to understand why the wind at the latter place
hardly shows this variation.*

It is in this stratum of moving air that the thunderstorm
cumuli are borne along, so that this stratum must reach at
least 5 or 6 miles above the surface ; and it is curious to
watch the heavy thunder-showers at Lucea sweep up from
the south-east in the summer months w^liile the sea-breeze is
often blowing hard from the north-east.

At sea this easterly trade-wind moves at the rate of about
240 miles per diem ; at the Kempshot observatory this rate is
reduced to 142 miles per diem.

There are still two higher currents of air shown by the
upper cloud-drifts, to which reference will be made in the
following section.

Clouds and Cloud=drift

There has been considerable confusion among writers on
Meteorology in the naming and classification of clouds. Early
in the nineteenth century Luke Howard proposed a system
based upon the thi'ee primary forms cirrus, cumulus, stratus,
and their compounds cirro-stratus, and so on ; and probably
it was the w^ant of proper definitions of the forms and com-
pound forms which led to the confusion.

Recently there has been an international movement to-
wards uniformity in cloud nomenclature based upon Howard's
system ; and the International Committee have published a
valuable cloud atlas. It is therefore advisable to state what
clouds have hitherto been registered in Jamaica.

Between 1880 and 1895 the Weather Service in Jamaica
followed the Instructions to Ohservers of the United States
Signal Service —

" Clouds will be recorded on a scale of from zero to ten,
zero being clear, and ten cloud}^

* Mr. E. Johnstone suggests tlie Blue Mountain range to the north of the
Plantation, the range running east and west.

26 THE METEOROLOGY OF JAMAICA

**Tlie following will be recorded as upper clouds — cirrus,
cirro-stratus, cirro-cumulus, and cumulus.

*^ The following will be recorded as lower clouds — cumulus,
stratus, cumulo-stratus, nimbus, and fog.

"Cumulus maybe reported either as upper or lower clouds,
depending upon the position they occupy."

It w^as soon found that the clearest months of the year
are January, February, and March, when on an average
three-tenths of the sky are obscured ; and that the cloudiest
months of the year are August, September, and October, when
on an average six-tenths of the sky are obscured.

Also it was found that the upper clouds are for the most
part only seen from June to October inclusive, and during
those months only in the early morning, as a rule ; and that
the lower clouds are seen during midday all the year round.

From January, 1896, onwards the clouds were divided
into upper, middle, and lower, following the primar}^ forms
of cirrus, cumulus, and stratus. This was necessary for the
following reasons : — cumulus in Jamaica is often 6 miles
high, reaching from the rain falling on the ground to the
upper regions of cirrus ; and, during the hurricane months,
clouds of the cirrus class move from the east-north-east ;
clouds of the cumulus class move from the south-east ; and
clouds of the stratus class according to local circumstances
of sea-breeze, land-breeze, and mountain configuration ; and
for storm -warning purposes the importance of such generali-
zations cannot be over-estimated.

Moreover, the nomenclature was brought into accordance
with the system adopted b}^ the International Committee;
and in Weather Ileport No. 193 a full account of these
changes was given. It will here be sufficient to describe the
different clouds as distinctly as possible.

(1) Cirrus. — This cloud consists of long fibrous threads,
often blown by the upper currents into such forms as feathers,
mares' tails, etc. When the threads or feathers point towards
the observer, they appear like w^isps of hay or straw. This
is the pure form of cirrus, and it is caused by the condensa-
tion of thin ascending streams of vapour, and b}^ the freezing
of the particles of water. These ice-clouds are often at great
elevations ; from the rate of decrease of temperature with the

CLOUDS AND CLOUD-DRIFT 27

height above the sea-level it appears that the freezing-point
of water is reached at an elevation of about 3 miles ; this
height is therefore the lower limit of cirrus over Jamaica.
As already said, cirras is often seen in the morning about
sunrise during the summer and autumn months, but they
rapidly disappear as the temperature of the day increases.
Under these circumstances they are fine-weather clouds, and
it is only when they increase in extent and develop into cirro-
stratus that they can be connected with bad weather.

According to the following table, there is a well-marked
upper current from the east-north-east during the autumnal
months —

North

North-east

East

South-east

South

South-west

West

North-west

Average drift of
Cirrus. Cirro-stratus.

7

... 9

2G

... 25

28

.. 27

8

... 18

4

... 6

FT

i

.. G

13 .

.. 5

7

.. 4

100 100

The numbers given in this table refer to a long series of
observations at Kempshot, and express the fact that out of
100 observations where the cirrus-drift was observed, 7 times
the drift was from the north, 26 times from the north-east,
and so on ; and similarly for cirro-stratus.

The table also shows a still higher current from the west ;
and the existence of this current has been confirmed at times
by the drift of long continuing trails of shooting-stars, and
by the drift of dust from volcanoes in eruption.

(2) Cirro-stratus. — This cloud consists of thin sheets of
fibrous texture ; the threads often seem to interlace, when
the clouds appear to be woven. Solar halos, mock suns,
etc., are caused by the ice particles of which this cloud is
composed. Cirro-stratus is always found to surround the
advancing half of a cyclone ; and hence its importance in
forecasting the weather. The lower limit is the same as
that of cirrus ; it also shows the north-east current, but not
the hiojhest west current.

28 THE METEOROLOGY OF JAMAICA

(3) CiREO-cuMULus. — This cloud consists of thin sheets of
small and separate flakes, arranged more or less regularly
along|two sets of parallel lines. When seen at great elevation,
the arrangement resembles the scales of mackerel ; when seen
lower.]; down, the large size of the lozenge-shaped flakes give
the sky the appearance "of a gigantic chess-board." The
flakes have no fibrous texture, but the parallel lines refer
them to cirrus ; for long cirrus stripes are often striated, or
cut off into small and equal lengths, and if a number of such
stripes were placed side by side, we would have the form
but not the texture of cirro-cumulus. This may be some
apology for the word cirro ; but there can be little or none
for the word cumulus, because the new cloud alto-cumulus
is very similar to (3), with this difference, that the com-
ponent parts are soft rounded masses — small cumuli, in
fact.

(4) Strato-cirrus. — A cloud somewhat resembling cirro-
stratus, but thick and woolly. It is a tropical cloud, and
has not received much attention from the meteorologists of
northern latitudes.

When rain begins to fall from a large cumulus, a quantity
of cloud is poured into the air from the top of the cumulus,
as smoke from a factory chimney. This takes place in all
parts of the world when rain falls from cumuli, but in the
temperate zones only a little cirriform cloud is thrown off.
In Jamaica the process is on a gigantic scale, and the cloud
is sjDread out as a sheet far and wide, so as to shade the land
for some hours from the direct rays of the afternoon sun.
It is therefore a common cloud in the west-central district
of Jamaica during the summer and autumn months. Its
texture at first is thick and woolly, but as it spreads the
sheet becomes thinner. It then settles down, often passing
through different forms, and finally disappears, leaving the
evening sky perfectly clear.

Now, by means of a sextant, some careful observations were
made of the altitude of the tops of well-formed cumuli, whose
distances could be ascertained by their rain falling on
mountain ranges or by the average interval between the
distant thunder and lightning; and it was found that the
average height of such well-formed cumuli was as much as

CLOUDS AND CLOUD-DRIFT 29

6 miles ! At this elevation the temperature is below zero,
and strato-cirrus, when spread out as described above, must be
very fine ^now as distinguished from the very minute particles
of ice which form cirrus and cirro-stratus. This fine snow
then falls slowly by its own weight, and, melting, it often
produces those quiet after-rains which follow the heavy rains
and squalls of the cumulus.

From what has been said about the spreading out of this
cloud, it might be supposed that it had no average drift ; but
if well-formed cumuli at considerable distances be watched, it
will be found that while their average drift is from the south-
east over the western half of Jamaica, the drift of the strato-
cirrus issuing from them is generally north-east.

(5) Cumulus. — This cloud consists of large rounded masses
resting on flat bases ; it is often called the thunder-cloud.
Its texture is apparently very solid; and it is formed by
ascending columns of heated vapour. When rain falls from
the base of the cloud it is called—

(6) Cumulo-nimbus, and this rain takes up the drift of
the whole cumulus. The velocity of the wind accompanying
the rain is thus the same as the velocity of the whole cloud ;
and these squalls are sometimes very severe, especially on the
mountains.

(7) Alto-cumulus. — A thin sheet of small separate clouds,
arranged more or less regularly into groups or lines. The*
clouds are soft, rounded masses, like fleeces of wool, and the
whole cloud often resembles a flock of sheej). Its average
drift is from the south-east.

(8) Alto-stratus. — *'A thin sheet of a grey or bluish
colour, showing a brilliant patch in the neighbourhood of
the sun and moon, and which, without causing halos, may
give rise to coronae." Thick and thin are merely relative
terms; and this cloud is thin when compared with strato-
cirrus. It has a soft, watery look. It is not often seen
in Jamaica.

(9) Strato-cumulus. — *' Large globular masses or rolls of
dark cloud, frequently covering the whole sky, especially in
winter, and occasionally giving it a wavy appearance. The
layer of strato-cumulus is not as a rule very thick, and
patches of blue sky are often visible through the intervening

30 THE METEOROLOGY OF JAMAICA

spaces." The general appearance of this cloud is somewhat
similar to a Venetian blind, the dark and light bars being all
parallel to the horizon, wherever you look.

(10) Nimbus simply means rain-cloud ; and as w^e have
already had cumulo-nimbus, this form should certainly be
called strato-nimbus.

(11) Stratus. — ''A horizontal sheet of lifted fog. When
this sheet is broken up into irregular shreds by the wind, or
by the summits of mountains, it may be distinguished by the
name oi fracto-sti^atus."

Fogs lie during the night in the valleys in Jamaica,
especially in St. Thomas-in-the-Vale and in the interior parts
of Hanover, Westmoreland, and St. James, where those three
parishes join ; the morning sun dispels them about two hours
after sunrise, and if the morning be still and calm, a cloud
will be observed high above the valleys w^hich the fog had
previously filled. The above definition should be considered
to inchide ani/ loio horizontal sheet of smoke-like cloud condensed
out of lifted invisible vapour. In consequence,

(12) Fracto-stratus is the commonest cloud in Jamaica,
winter and summer alike. In summer it develops into
cumulus ; in winter it develops into cumulus, stratus, or
strato-cumulus.

Clouds (1) to (4) inclusive belong to the upper division ;
(5) to (7) inclusive belong to the middle division ; and of
course (8) to (12) inclusive to the lower division.

In the Eegister their order should be reversed, so that the
column containing the lower cloud should follow the column
containing the surface wdnd ; then the middle cloud, and
then the upper. For there is a well-known law respecting
the relative direction of a succession of currents ; * and it is
convenient to see at a glance whether cyclonic (or anti-
cyclonic) conditions prevail among the currents ; for though
these conditions seldom occur, yet the importance of keejDing
careful watch for cyclones is so great that an observer should
regulate his system accordingly.

* lu the northern hemisphere, if you stand with your back to the wind, the
higher currents will come more and more from the left (or diverge more and
more to the right), the higher the currents are. This law applies to both
cyclones and anticyclones.

CYCLONES 31

Cyclones

AYhen the barometric pressure over a raore or less circular
area of sea or land is less than the pressure over the surround-
ing sea or land, the pressure diminishing from the outside
towards the centre, and when the winds rotate about the
centre, the whole mechanism is called a cyclone ; and in
the northern hemisphere the motion of rotation is opposite
to that of the hands of a watch.

The above definition includes tornadoes, or violent whirl-
winds, where the diameter of the disturbed area is compara-
tively very small ; but as we have no tornadoes in Jamaica,
we must confine our attention to cyclones properly so called,
with diameters of 100 or 1000 miles.

At the centre of a cyclone there is a calm area generally
5 or 10 miles in diameter ; and while the winds rotate round
this calm area they are somewhat drawn in towards it ; and
the following is the rule to find approximately the direction in
which the centre lies : — stand with your back to the wind, and
the centre will lie in a direction between your left hand and
your face. The rule respecting upper currents was given at
the end of the last section on clouds and cloud-drift.

The whole cyclone may be stationary, or it may move on
its course over sea and land with a velocity more or less
uniform, seldom exceeding 10 or 15 miles per hour in the
West Indies.

The fall of pressure at the calm centre may be very
small — say one-tenth of an inch — and then the rotating
winds will be very gentle ; or it may be large — say one
inch — and then the rotating winds may be violent, especially
towards the calm centre ; but the strength of the wind really
depends on the barometric gradient, or the fall in pressure
per mile of approach towards the centre.

It will be convenient to call the former cyclonic depressions,
and to restrict the term " cyclones " to storms dangerous to life
and property.*

The general principles given above apply to cyclones all

* OtherwiBe called " liurricanes," the term applied to them before their
cyclonic nature was known.

32 THE METEOROLOGY OF JAMAICA

over the northern hemisphere, and they are quite intelhgible ;
but when we come to details it would seem that there is much
we have yet to learn ; and it is here proposed to give the
result of twenty-five years' experience in Jamaica in connec-
tion chiefly with the Weather Service.

(1) Depressions often pass near or over Jamaica at all
times of the year ; they often throw down immense quantities
of rain ; and all our flood-rains are due to such depressions,
or to cyclones proper, the latter being very few and far
between. From June to November their course is the same
as that of cyclones proper, namely, west-north-west ; from
December to May their course is in an opposite direction,
namely, east-south-east. Some of the former develop into
cyclones, as on October 15 and 16, 1897 ; some of them are
''northers," which occur during the winter months, and get
mixed up with the effects of the anticyclone over the United
States ; and others throw down enormous quantities of rain.
The June floods of 1886 were due to a depression which passed
near Jamaica, where the fall of pressure could not have exceeded
0'15 inch ; and these rains were far in excess of those thrown
down by the more developed cyclones of 1880 and 1886, which
both crossed the island.*

(2) When a cyclonic depression is generating it is station-
ary, or nearly so ; after a time it moves off, and may develop, or
diminish and disappear. The June depression, 1886, is a good
example. On the 5th and 6th it was generating south-east of
Kingston ; on the 7th it started on a course parallel to a line
joining Kingston and Montego Bay at the rate of 10 miles an
hour; so that, if instead of generating for two days and a half
it had been advancing towards Kingston, its diameter must
liave been 1200 miles, which is out of the question with such
a small fall at the centre. A better example occurred on
October 26, 27, and 28, 1899. The barometric pressure at the
Kemp shot observatory gradually fell, and the wind from the
south gradually increased in strength with torrents of rain,

* The followinc: depressions give further examples : —

1885, December 1, 2. 1898, May 23, 27.

„ December 26, 27. 1899, October 2(3, 27, 28.

1888, May 8 to 15. „ November 8.

„ September 3.

CYCLONES 33

plainly showing that a depression was being generated between
Jamaica and the Cayman Islands, where several other de-
pressions have been noticed to generate (or to develop) before.
On the afternoon of the 28th the depression suddenly started
on its course, at first north-east, and then north, according to
subsequent news.

In these and other cases the records show no unusual
features immediately before the generation of the depressions.
The wind, the rain, and the fall of pressure all take place
together as a matter of course.

(3) Fully developed cyclones appear in the West Indies
for the most part during the months of August, September,
and October only; they follow a west-north-west course at
first, then they turn north, and finally recurve east-north-
east, if their course is long enough to permit of these changes.

If we look at the Pilot Charts published each month by
the United States Hydrographic Office, we shall see that when
the region of equatorial heavy rains between South America
and Africa reaches as far north as latitude 15 , cyclones
originate in about that latitude, but to the west of the region
of heavy rains, and then move ofl: on a westerly course. As
the diverting efiect of the earth's rotation upon currents of air
is very important for the development and maintenance of
cyclones, and as this effect varies as the sine of the latitude,
there are no cyclones near the equator, or within 12" of it ;
but, as we have seen at 15^, the effect is sufficient to give the
currents the necessary divergence. Now, as the region of
heavy rains advances as far north as latitude 15^ in August,
somewhat farther in September and October, but withdraws
far to the south in November, and remains there until the
following July, it is evident that August, September, and
October are the months in which cyclones usually occur in
the "West Indies. Of course, they may occur at other places
and at other times if all the essentials are present and
combine.

With regard to the course taken by cyclones, no doubt they
follow the general atmospheric drift, and move round the
anticyclone in the North Atlantic ; a large number pass over
the Bahama Islands, and a few pass over the Caribbean Sea.
Both the hurricanes of October 3, 1780, and August 18,

34 THE METEOROLOGY OF JAMAICA

1880, were passing south of Jamaica when they turned north
and swept the island.

(4) When a large cyclone has developed, it often happens
that a cyclonic depression makes its appearance and confuses
the indications. For instance, in September, 1883, a large
cyclone advanced through the Mona Passage on its course to
the United States, and at the same time a depression passed
south of Jamaica on a westerly course; and the Weather HcporU
contain a number of such cases.

(5) The rules given above as to the rotation of the wind
and upper currents round the centre are more than useful as
generalizations ; but in forecasting they must be used with
the greatest caution, especially when the cyclone is at a
considerable distance. On the other hand, much more use can
be made of the barometer than in the temperate zones, where
the fluctuations are large, provided that every care be taken
in its management, as detailed in the first section.

(6) Finally, there is a cyclonic feature often noticed in
Jamaica, of which we have seen no account given elsewhere —
after a cyclone has passed and is moving away, it draws after
it our winds and clouds for one or two days. To whatever
cause this effect may be attributed, it is very useful in letting
us know in what direction the cyclone has gone.

In conclusion, a list of the more important articles among
the Wcatlicr liejxrrts is added, to which the reader may refer
for further information than could be given in the above brief
summary of Jamaica Meteorology.

Weather lleport

No.

Anemometer, the Kingston

200

Barograph „ „

192

Blue Mountain Peak observations

75

Clouds, classification of

193

Conflicting cyclones, 1889 (September 15)

109

Cyclone of 1880 (August 18)

In trod. Vol.

I.

„ „ 1886 (August 20)

09

Cyclones as observed in Jamaica

97

Earthquakes, reports on

4,77

Flood-rains, 1886 (June)

G7, 68

„ „ 1897 (October)

219

Gravity, standard ...

Introd. Vol.

Ill

Hurricanes, etc., notes of, up to 1880

„ Vol.

II.

CYCLONES

35

Lightning, protection of buildings from
Magnetic declination at Kingston ...
Meteorological results, 1880-1890 ...

„ stations in Jamaica
Northers, list of
Eainfall, 1870-1879

„ 1870-1889

„ 1870-1899

Eains, list of heavy

Temperatures at Kingston, 1881-1898

,, list of low

Temperature, liainfall, and' Sun-spot per

Thunderstorms

Tides in Kingston harbour ...

AVeather Service, work done by ...

iod

Weathpr Report
No.

13G

133, 182

123

237

222

31,33

124 (a)

256 (a)

219, 226

275

222

275

193

227

237

36

THE METEOROLOGY OF JAMAICA

TABLES

TABLE I.

{Subtradive.)
Keductiox of the Barometer to 32° Fahr.

Attached

Height of the barometer

m inches.

thermom.

30

29

28

27

26

o

60

-0-085

ill.

-0-082

in.

-0-079

in.

-0-076 — 0-

in.

073

61

•087

•084

•081

•078

075

62

•090

•087

•084

•081

078

63

•093

•089

•086

•083

080

64

•095

•092

•089

•086

082

65

•098

•095

•091

•088

085

66

•101

•097

•094

•090

087

67

•103

•100

•096

•093

089

68

•106

•102

•099

•095

092

69

•109

•105

•101

•098

094

70

•111

•108

•104

•100

096

71

•114

•110

•106

•102

099

72

•117

•113

•109

•105

101

73

•119

•115

•111

•107

103

74

•122

•118

•114

•110

106

75

•125

•120

•116

•112

108

76

•127

•123

•119

•114

110

77

•130

•126

•121

•117

112

78

•133

•128

•124

•119

115

79

•135

•131

•126

•122

117

80

•138

•133

•129

•124

119

81

•141

•136

•131

•126

•122

82

•143

•138

•134

•129

•124

83

•146

•141

•136

•131

•126

84

•149

•144

•139

•134

•129

85

•151

•146

•141

•136

131

86

•154

•149

•144

•138

133

87

•157

•151

•146

•141

■136

88

•159

•154

•149

•143

•138

89

•162

•156

•151

•146

•140-

90

-0164

-0-159

-0-153

_ 0-148 -0

142;

TABLES

37

TABLE II.

{Additive^

Eeduction of the Barometer to the Sea-level.

Elevation

above
sea-level.

Temperature of the air at

sea-level.

70° •

75°

80°

as*

90°

Feet.

in.

in.

in.

in.

in.

100

+ 0-105

+ 0-104

+ 0-103

+ 0-102

+ 0-101

200

0 210

0-208

0-206

0-204

0-202

300

0-314

0-311

0-308

0-305

0-302

400

0-418

0-414

0-410

0-406

0-402

500

0-522

0-517

0-512

0-.507

0-502

000

0-G25

0-6-20

0-614

0-608

0-602

700

0-728

0-722

0-715

0-708

0-701

800

0-831

0-824

0-816

0-808

0-800

000

0-034

0-026

0-017

0-008

0-809

1000

1-03G

1-027

1-017

1-007

0-008

1100

M38

1-127

1-117

1-106

1-006

1200

1-240

1-2-28

1-217

1-206

1-105

1300

1-341

1-3-20

1-317

1-305

1-203

1400

1-442

1-4-20

1-416

1-403

1-300

1500

1-543

1-520

1-515

1-501

1-488

2000

2-042

2-0-24

2-006

1-089

1-972

2500

2-534

2-512

2-400

2-469

2-449

3000

3-019

2-003

2-067

2-043

2-919

3500

3-407

3-467

3-438

3-410

3-382

400(»

3-0G7

3-034

3-002

3-870

3-839

4500 1

4-432

4-305 ;

4-350

4-324

4-289

5000

4-800

4-840 i

4-800

4-770

4-731

5500

5-342

5-206

5-252

5-200

5-167

GOOO

5-788

5-738

5-680

5-642

5-507

6500

6-227

6-173

6-120

6-060

6-010

7000

6-GGO

6-601

6-544

6-488

6-433

7500

1

+ 7-088 \

1

+ 7-024

+ 6-062

+ 6-000

+ 6-840

.^8

O

o

a

o

d

03

OQ

d

02

O

CO

o
o

I— I

K

-<)

C3
P

M
O

o

1-4

O

o

o

1—1

I

o

03

©

d

©
©

d

03
U

a

d

os"
©

c3

c3

O
fa

•ra-d II

r-i(M(M(MC<IC<I(MCO(MC^i— iC^
1 1

CO

1

•ra-d 01

COCOCOrHOO'-H-MCiOiOiOCO
1 1

1

•ufd 6

1— (r-(i-li-li-lr-lr-lr-l<M(MCqcM
1 1

05
rH

1

•tn*d 8

GOCDOQ;— (,— llOCOC<JCOC<lCOr-l
1 1 1 + 1 r-H rH rH

13
1

•tu'd i

COCOiOCOtOrHCiiOCOOCOirs
_Ll— 11 — li—li—lt— I I— 11— 1 1

•tn-d 9

(M(M(MCOCOCMCMC:^<M(M(M(M

+ +

+

•ra"d g

coTfHcoTtiTiHco(>4Coo':coci-:co
+ +

CO
CO

+

•ra-d t

»Ot>»OlOCC10<TOlOi— lO-^iO

TKTtl^'flrtlOOCOCO^COTjHT+H

+ +

+

•ra-d g

CSQOCOOOCOC^t^i-lOI-OO
+ +

05
CO

•ra-d 5

rHTHOCOOCOOOC5-HOir-l
'<tlCOCOC^<MT-l(NC<J(MCOCO'*

+ +

+

■ra-d I

(M I— 1 I— 1 I— ( (M CM I— 1
+ + +

•uoojsj

i>cot>»oiCTHa:cqi-(i>ioo

1 rH i-H 1— • T-H 1— ( I—I 1—1 1

rH
rH

1

•ca-B IT

rHi>co— ic:icocoor>oi(M-H

COCCCOCOC^ICMrHC^CMlMCOCC
1 1

o

CO

1

•ra-B 01

coi-ioooocioqajcoTtioos

1 1

o

1

•m-e 6

i-(COI>(MCOI>rHOOOi— l(M

1 1

o

1

•ra-B 8

OOCOCOCOCOtMi-ir-HCMtNCOO:)

1 1

o

CO

1

•ra-B i

r-irH<MC<l(Mi— 1 r— It— (i— l(Mi— 1

1 1

1

•ra-B 9

i-lrHOI>Oi-iCCCO<M--l»ni-l

1 II 1 1 1 + + 1 + 1 1

(M

1

-ra-B y

1— i-*c5oococc»oc':o5cO'-^c^

rH r— 1 rH f-H rH r^ r^ rH

CO

+

-ra-B f

0__t>CO»Ol>t^l>rHrHO OJ

i-^C^JOarHrHrHrHrHrHCNC^CN '-'
+ + i +

-ra-B s

t>-JlOOOOCOCOOrHCOrH ^
rH(MC^(M(MrH-— ii-irH(M(M(N J5

+ + 1 + ,

-ra-B r.

Oi-*CiirS->^<MrH05050l>i-H 1 CO
IrHrHrHrHi— (T— 1 i— IrHrH i— i

+ ; +

•ra-T? I

(MOlO(Nr-lrH-»tlTtHCO»OtOCO
1 + + + + 1 1 1 + + 1

o

-VlSiupii\[

rHt>c;C5COOi:-C5Cir^co<M

rHrH rHi-Hr—irHi— irH i-H
1 1

CO

1

^ S «3 ©

^ ^ ^ -g t- rQ ^

G ^ h <- ^dr^='-a.-M > ©

•
•
•

m

a
a
©

^ 1

©
c3

OS

o

o

^

TABLES

39

TABLE IV.

Kingston

ME.ix Prkssure at Sea-level.

inches.

inches.

Jan. 1 to 10

.. 20-08 1

Julv 1 to 10

20-058

„ 11 „ 20

•001

,; 11 „ 20 .

-061

„ 21 , 31 ... .

•001

„ 21 „ 31

^050

Feb. 1 „ 10

•080

Aug. 1 „ 10

^035

„ 11 „ 20 ... .

•086

„ 11 „ 20 .

^020

„ 21 „ 28 ... .

•083

„ 21 „ 31

•ooo

Mar. 1 „ 10

•078

Sept. 1 „ 10

-000

„ 11 „ 20

•071

„ 11 „ 20 .

-803

„ 21 „ 31

•0G5

„ 21 „ 30

-885

Apr. 1 „ 10

•055

Oct. 1 „ 10

-878

„ 11 „ 20

•045

„ 11 „ 20

-874

„ 21 „ 30

•033

„ 21 „ 31

-875

Mav 1 „ 10

•022

Nov. 1 „ 10

-885

,; 11 „ 20

•OIG

„ 11 „ 20

^800

„ 21 , 31

•010

„ 21 „ 30

^012

June 1 „ 10

•027

Dec. 1 „ 10

-027

., 11 „ 20

•037

„ 11 „ 20

^042

„ 21 „ 30

.. 20-040

„ 21 „ 31

20-061

The numbers for the middle of each month were taken from Weatlier
Beport Xo. 123, and they are the means deduced from ten years' observa-
tions at the hours 7 a.m., 3 p.m., and 11 p.m. The other numbers were
found from a curve drawn througli the numbers at the middle of each month.

^lean pressure at Kingston sea-level for the year = 20*036 inches.

40

THE METEOROLOGY OF JAMAICA

TABLE V.
Sujvimary of the Kingston Monthly Temperatures, 1881-1898.

Average

Average

Month.

Mean,

7 a.m.

3 p.m.

Max.

Min.

highest
max.

lowest
min.

o

o

o

o

o

o

o

January ...

75-8

68-9

83-1

86-1

67-0

90-1

62-8

February

75-7

69-4

82-7

85-6

67-0

89-3

63-2

March

76-4

71-3

82-8

85-6

67-8

89-3

63-9

April

78-2

74-9

83-3

86-3

70-0

90-1

66-6

May

79-9

78-1

83-7

87-0

72-5

90-2

68-9

June

81-1

79-1

85-2

88-2

73-7

91-8

70-4

July

81-6

78-7

86-4

89-5

73-4

93-4

70-4

August ...

81-0

77-6

85-7

89-5

73-4

92-6

70-2

September

80-7

7G-9

85-2

89-2

73-5

92-3

70-7

October ...

79-3

75-6

84-5

88-0

72-4

91-8

68-8

November

78-6

73-4

84-3

87-9

70-7

91-1

66-6

December

76-9
78-8

70-7
74-6

83-3

86-7

68-4

90-5

63-7

Means, 18 years'"!
observations /

84-2

87-5

70-8

91-0

67-2

TABLE VL
Average Annual Temperatures at Different Elevations in Jamaica.

Elevation

above

Mean.

Max.

Min.

Range.

Bea-level.

-

Feet.

o

o

o

o

0

78-8

87-5

70-8

16-7

500

77-1

85-1

69-8

15-3

1000

75-3

82-8

68-6

14-2

1500

73-6

80-6

67-4

13-2

2000

72-0

78-6

66-1

12-5

2500

70-3

7G-7

G4-7

12-0

3000

68-7

74-9

63-3

11-G

3500

67-1

73-2

61-7

11-5

4000

65-5

71-6

60-1

11-5

4500

64-0

70-1

58-5

11-6

5000

62-4

68-8

56-8

12-0

5500

61-0

67-5

55-0

12-5

6000

59-5

66-3

531

13-2

6500

58-0

65-2

51-2

14-0

7000

56-5

64-3

49-3

15-0

7600

55-1

63-0

47-3

lG-3

TABLES

41

<

O

QQ

05
!5
t-i

P
»

El

o

z
o

Eh
■<

>

<

«

P5
O

o

t-H

O

OS
P3
O

•in"d II ] + o ^

'in'« II

I o

•ra-B 01

•OIB 6

O C- rH t^

-M CO

l> C^ GO p 1-- t^ to

CO CO r: -+1 th <N c<i

•m-B 8

o CO

+

p p

+

o
o

I

^lQO(NpT-IC<It»CO

III I I + +

•ra"« z,

+ o

«)

t^»-Ht>ot>pi-(cppQoqo
oiiTt<r^cbTHTtHOTcbTt<»b

•UI'B I-

10

(M

(?1

GO p

lb »b

p p

CO CO

CO o

•ra-BC

a. c "^

O

cb

C5

10 »o
CO lb

o 00
»b >b

CO Oi

•ra*? z

•lU'B I

+ O V

UOl

+ o»

t- l>

»b >b

»b

lb »b

CO CO

»b »b

CO CO

rt< op

>* »b

■^qSinpiiY

1 CO

OS t>

CO

CO o

CO l>

05 O
CO rt<

05 ""^

CO tH

c
o

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03

hJ r^ S <1 § t-5

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=3 9

9 O

1-3 <5

GQ O

o

a

o

>
c

o

a

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;^.o

•ra-d 01

+ 0=P
CO

CO

C<l

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(7Q

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CO

CO

1-H

CO

p

CO

p
CO

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I-H

CO

•ra'de

+ °g

0^

p

1-^

99

1—1

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l-H

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c<>

0

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I^
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•ra"d 8

-«^

b

b

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b

b

b

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00

•

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1-H

I-H

CO

l-H

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OS

b

•ra*d 4

(M

ob
+

1

p

7

00

7

0

b

1

b
1

1

b
1

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b
+

00

b
+

10

b
+

b
+

b

1

•ni'dg

1 0^

(M

i>

r-t

CO

0

C<J

T-H

CO

(f<l

lyH

CO

b

00

b

CO

I^

0

GO

•ca-d g

1 oP

•0
0

CO

C5

CO
CO

CO

00

CO

I-H

CO

0

00

CO

•ra-d t

' °s

CO

cb

0

p

0

I-H

CO

10

CO

CO

CO

ib

GO

•m-d e

' °g

p

cb

uo

lb

CO

CO

CO

lb

0

»b

0

0
«b

b

10

lb

•ra-d s

1 o'P

p

b

CO

b

p

»b

0

CO

0
b

C<J

lb

lb

b

0

•

t>

CO

b

•ra-d I

1 oW
00

l-H

00

0

cb

CO

b

in

b

b

rH

1.0

b

b

00

b

00

0

-aoox

00

CO

0

b

crs
b

I-H

0

C5

b

CO

b

CO

CO

00

b

lb

CO
CO

b
+

00

-lUB 9

+

op

CO

-tl

t-

1—1

—

^^

■^

CO

0

c^

C5

p

CO

CO

-0

CO

—

CO

b

b

0

CO

■^

»b

b

•ra-«s

+

ogs

"*

-«*<

rH

a

I>

GO

CO

l-H

tH

p

p

00

tn

CO

CO

CO

ITS

10

b

b

in

lb

TtH

ib

lb

»b

>b

GO

lb

■*

C>1

GO

00

a

0

0

0

GO

r-l

CO

00

0

LO

't"

^

Ttl

0

0

•<*<

■*!

tH

"*

tH

e3

as
;h

P
O

-4-3

o

2
o

©
o

>4

O

o

fH

o

a

o

O

34

as

o
o

o

o

42

THE METEOROLOGY OF JAMAICA

TABLE YIII

Temperature.

Tension of saturated
vapour.

Glaisher's factors.

o

inches.

60

0-518

1-88

61

0-537

1-87

62

0-556

1-86

63

0-576

1-85

64

0-596

1-83

65

0-617

1-82

m

0-639

1-81

67

0-661

1-80

68

0-684

1-79

69

0-708

1-78

70

0-733

1-77

71

0-759

1-70

72

0-785

1-75

73

0-812

1-74

74

0-840

1-73

75

0-868

1-72

76

0-897

1-71

77

0-927

1-70

78

0-958

1-69

79

0-990

1-69

80

1-023

1-68

81

1-057

1-68

82

1-092

1-67

83

1-128

1-67

84

1-165

1-66

85

1-203

1-65

86

1-242

1-65

87

1-282

1-64

88

1-3-23

1-64

89

1-366

1-63

90

1-410^

1-63

TABLES

43

TABLE IX.
Tj::mpekatuee of the Dew-poixt.

Dry

Difference between the dry and wet bulbs.

bulb.

1°

2°

3°

49

5°

6°

7°

8=

9=

10°

o

60

o

58

o

56

o

54

o

52

o

51

o

o

o

o

o

61

59

57

55

54

52

50

62

60

58

56

55

53

51

—

63

61

59

58

56

54

52

50

64

62

60

58

57

55

53

51

—

65

63

61

60

58

56

54

52

50

66

64

62

61

59

57

55

53

52

50

67

65

63

62

60

58

56

54

53

51

68

^'o

64

63

61

59

57

56

54

52

50

69

67

65

64

62

60

58

56

55

53

51

70

68

60

65

63

61

59

58

56

54

52

71

69

68

^^

64

62

60

59

57

55

53

72

70

68

67

65

63

62

60

58

56

54

73

71

70

68

6G

64

63

61

59

57

56

74

72

71

69

67

65

64

62

60

58

57

75

73

72

70

68

66

65

63

61

60

58

76

74

73

71

69

67

66

64

62

61

59

77

75

74

72

70

68

67

65

63

62

60

78

76

75

73

71

70

68

66

64

63

61

79

77

76

74

72

71

69

67

6Q

64

62

80

78

77

73

72

70

68

66

65

63

81

78

76

74

73

71

69

68

66

64

82

77

75

74

72

70

69

67

65

83

^^

78

76

75

73

71

70

68

66

84

<~~

77

76

74

72

71

69

67

85

78

77

75

73

72

70

68

86

78

76

74

73

71

70

87

77

76

74

72

71

88

II

—

78

76

75

73

72

89

_^_

1

^

78

76

74

73

90

—

—

—

77

75

74

44

THE METEOROLOGY OF JAMAICA

TABLE X.

«

Humidity.

Dry

Difference between the dry and wet bulbs.

bulb.

1°

2°

3°

4°

76

5°

6°

7°

8°

9°

10°

o

60

94

88

82

71

61

94

88

82

77

72

67

62

94

88

82

77

72

67

63

94

88

82

77

72

67

63

64

94

88

82

77

72

67

63

65

94

88

83

78

73

68

63

59

—

66

94

88

83

78

73

68

64

60

56

67

94

88

83

78

73

68

64

60

56

52

68

94

88

83

78

73

68

64

60

56

52

69

94

88

83

78

73

68

64

60

56

53

70

94

88

83

78

73

69

65

61

57

53

71

94

88

83

78

73

69

65

61

57

53

72

94

89

84

79

74

69

65

61

57

54

73

94

89

84

79

74

70

m

62

58

54

74

94

89

84

79

74

70

^^

62

58

55

75

94

89

84

79

74

70

m

62

58

55

76

94

89

84

79

75

71

67

63

59

55

77

94

89

84

79

75

71

67

63

59

56

78

94

89

84

79

75

71

67

63

59

56

79

95

90

85

80

75

71

67

63

59

56

80

95

90

85

80

75

71

67

63

59

56

81

90

85

80

76

72

68

64

60

56

82

85

80

76

72

68

64

60

57

83

85

80

76

72

68

64

60

57

84

80

76

72

as

64

60

57

85

80

76

72

68

64

61

58

86

76

72

68

64

61

58

87

73

69

65

61

58

88

73

69

65

61

58

89

5-

69

65

61

58

90

1

65

62

5,9

TABLES

45

TABLE XI.
Dew-point aio) Humidity at Kingston.

Month.

Dew-point.

Min.

Humidity.

Janimiy

G6-7

o

66-8

78

February

6(>7

66-8

78

March ...

C7-G

67-8

77

April ...

69-1

69-8

75

May ...

71-4

72-4

78

June . . .

72-8

73-8

78

July ...

72-5

73-5

76

August

73-0

73-2

79

September

73-1

73-3

80

October

72-2

72-1

81

November

70-1

70-7

78

December

G8-0

68-4

78

Mean

70-3

70-7

78

The above table contains the results of observations between June, 1880,
and May, 1890, inclusive ; the figures for the Min., therefore, sHghtly differ

(Weather Beport, No. 123.)

from the figures in Table V.

46

THE METEOROLOGY OF JAMAICA

TABLE XII.

The Jamaica Monthly Kainfall.

Year.

Jan.

Feb.

Mar.

Apr.

May.

June. July. Aug.

Sept.

Oct.

Nov.

Dec.

Total.

in.

in. in.

in.

in.

in. in.

in.

in.

in.

in.

in.

in.

1870 ...

3-99

4-35 3-10

2-79

17-38

3-58 4-33

5-72

8-05

16-74 12-50

6-90

89-43

1871 ...

2-40

1-60

2-29

3-46

6-43

1-98 3-79

3-46

5-70

8-88

5-88

4-22

5009

1872 ...

3-00

2-84

3-06

2-06

5-18

2-41

2-89

5-24 4-55

6-09

3-13

4-73

45-18

1873 ...

815

1-94

5-47

1-15

5-06

2-58

2-56

7-51

10-73

8-57

3-53

5-81

63-06

1874 ...

3-44

2-20 '0-61

4-40

10-65

3-96

2-51

9-65

6-82

11-69

10-52

2-49

68-94

1875 ...

2-57

0-67 2-59

3-05

8-54

3-74

3-87

5-13

7-60

5-58

2-34

6-74 i 52-42

1870 ...

6-00

0-96 1-63

4-68

8-24

5-40

8-15

5-06

5-19

11-36

8-96

5-72

7135

1877 ...

5-94

1-18 5-38

291

15-03

6-50

4-68 1 1-76

5-01

4-50

7-63

7-88

68-40

1878 ...

G-35

2-80 ;2-78

0-70

4-86

6-63

5-85 10-80

7-43

11-29

7-32

9-61

76-42

1879 ...

2-81

5-30 6-49

7-28

9-14

10-64

4-47 12-32

7-38

15-96

5-29

1-76

88-84

Means ...

4-4G

2-38 3-34

3-25

9-05

4-74

4-31 6-66

6-85

10-07

6-71

5-59

67-41

1880 ...

4-36

0-96

1-10

2-77

11-60

3-09

3-86 9-58

3-97

400

2-21

7-94

55-44

1881 ...

1-22

4-01

1-30

4-63

10-28

5-56

4-77 6-21

7-68

12-08

7-52

3-34

68-60

1882 ...

2-92

1-93

3-54

3-32

8-22

2-33 3-76 4-80

8-78

8-96

5-36

3-95

57-87

1883 ...

5-49 3-50

4-08

3-34

5-29

4-98 13-15 5-42

7-82

8-15

5-12

2-92

59-26

1884 ...

4-72 3-44

2-51

1-85

6-72

6-89

2-52 5-06

6-23

9-52

5-00

2-44 56-90

1885 ...

1-73

1-49

1-47

4-73

4-90

3-32

301 619

6-22

6-37

4-74

15-69 59-86

1886 ...

5'23

4-65

2-68

6-39

5-30

23-36

6-22 13-54

5-90

7-98

3-70

5-66 90-61

1887 ...

6-02

2-32

2-38

4-47

9-32

8-89

7-19

6-91

5-77

8-47

8-17

0-75 70-66

1888 ...

1-36

1-89

1-70

3-61

21-24

6-77

2-(;5

5-47

8-10

4-38

4-59

10-35 72-11

1889 ...

4-78

0-90

4-19

249

6-71
4-18

7-82

12-52

6-08 5-12

8-20

10-49

4-37

2-97 74-15

Means . . .

3-78

2-51

9-07
5-57

7-77

4-32 6-83

6-87 8-04

508

5-60

66-54

1890 ...

5-21

2-92

5-84

3-37

413

4-99 6-92

6-52

7-04

6-52

5-39 64-42

1891 ...

3-45

2-24

0-84

8-49

12-28

9-91

5-57] 7-45

6-35

15-32

7-65

5-15

84-70

1892 ...

400 1-38

2-27 2-82

8-53

7-31

4-44' 7-65

8-86 1217

9-96

3-61

73-00

1893 ...

344 3-24

1-92 5-42

10-90

7-20

9-15 6-72

7-92 10-30

10-10

10-18

86-49

1894 ...

205 2-52

3-33 5-84

16-64

3-90

5-92 4-20

6-98 12-40

505

6-56 75-39

1895 ...

1-31 500 i218 611

9-90

3-66

4-99 8-11

6-87 11-98

7-72

3-79 71-62

1896 ...

5-25 4-86 i4-28 3-67

9-96

4-84

5-03 4-74

8-24

7-51

4-57

5-66 I 68-61

1897 ...

0-88 0-77

1-82 7-06 10-91

4-92 5-92 6-55

10-13

19-26

5-73

3-64 77-59

1898 ...

1-75

3-93

1-26 4-09 |l6-76

7-60;6-50 6-92

7-10

10-38

4-78

2-75 73-82

1899 ...

3-96

2-84

3-76 4-80

4-20

4-66 3-86 4-22

7-44

2372

14-99

7-37

85-82

Means ...

313

2-97
4-15

2-75 '517

10-56

5-81

5-64 i 6-35

7-64

13-01

7-71

5-41

76-15

1900 ...

5-20

2-42 '5-67

7-77

616

1
7-18 5-38

8-12

6-50

5-22

5-88 69-65

1901 ...

3-91

117

3-32 2-57

6-13

1403 7-59 6-49

10-60

9-76

10-02

5-37 80-96

1902 ...

5-68

300 4-24 5-40

8-97

10-28 3-44 5-39

5-89

7-19

5-60

8-23 73-37

1903 ...

1-94 140 '319 4-90 '10-63

1

600 4-30 12-79

5-34

7-28

5-78

4-83 68-38

TABLES

47

TABLE XIIT.

AnNU^VL PiAIXFALL FOR EACH PtAIXFALL DmSIOX IN J.iMAICA.

Rainfall divisions.

"iear.

N.E.

N.

w.c.

s.

ine island.

in.

in.

in.

in.

1870

110-60

83-09

102-98

61-07

89-43

1871

69-45

41-88

54-56

34-46

50-09

1872

59-42

40-79

51-50

29-02

45-18

1873

84-08

52-64

67-79

47-71

63-06

1874

97-18

68-25

62-97

47-35

68-94

1875

71-89

47-15

56-16

34-47

52-42

1876

90-38

.54-71

87-33

52-99

71-35

1877

100-72

56-53

64-06

52-27

68-40

1878

104-12

62-99

72-44

66-11

76-42

lo /y ... ...

122-55

65-44

87-54

79-85

88-84

Means

91-04

57-34

70-73

50-53

67-41

1880

76-37

47-01

64-91

33-47 1

55-44

1881 ... ...

91-24

49-42

75-32

58-42

68-60

1882 ...

65-48

43-76

78-59

43-67

57-87

1883

7-2-30

41-52

78-19

45-02

59-26

1884

69-00

41-87

73-10

43-63

56-90

1885

70-55

5-2-77

72-62

43-52

59-86

1886

126-61

60-98

88-21

86-64

90-61

1887

80-25

61-07

80-14

61-16

70-66

1888

98-00

54-42

70-43

65-58

72-11

looJ ... ...

99-81

56-82

75-94

64-02

74-15

Means

84-96

50-96

75-74

54-51

66-54

1890

75-09

48-29

89-91

44-41

64-42

1891

110-56

66-71

100-50

61-03

84-70

1892

101-55

58-10

8-2-05

50-29

73-00

1893

106-50

6317

108-66

67-65

86-49

1894

90-56

54-04

95-93

61-01

75-39

1895

97-38

56-35

85-38

47-36

71-62

1896

95-42

54-90

78-31

45-79

68-61

1897

93-95

58-25

95-46

62-67

77-59

1898

102-92

52-44

84-26

55-67

73-82

1899 ...

112-10

61-31

101-28

68-62

85-82

Means

98-60

57-36

92-17

56-45

76-15

1900

96-91

50-67

79-84

51-15

69-65

1901

107-88

64-18

87-31

64-50

80-96

1902

95-97

58-78

89-75

49-14

73-37

1903

88-46

51-05

82-83

51-17

68-38

48

THE METEOROLOGY OF JAMAICA

TABLE XIV.

TABLE XV.

Wind.

Pounds

U.S. Wind Scale.

Miles pel
hour.

5

10
20
30
40
50

pressure
per sq. foot.

0-1
0-3
1-3

3-0

5-0
8-0

Light

Gentle

Fresh

Brisk

High

Miles per
hour.

lto2

3 to 5

6 to 14

15 to 24

25 to 39

60
70

... 12-0
16-0

Gale
Storm

40 to 59

60 to 79

80

... 21-0

Hurricane ... 80 and upwards

90

... 27-0

100

... 33-0

110

... 40-0

120

... 48-0

TABL]

E XVI.

Diurnal Variation of

THE Wind in Kingston.

Miles

Miles

per
hour.

per
hour.

1 a.m.

... 1-9

1 p.m.

... ... ... •.» Oi2

2 ,

. 2-0

9

7-9

3 ,

. 2-0

3 „

7-4

4 ,

. 2-1

4 „

6-5

5 ,

. 2-1

^ „

5-3

6 ,

21

6 „

4-1

7 ,

2-2

7 „

31

8 ,

2-5

8 „

2-5

9 ,

3-7

9 „

2-1

10 ,

5-4

10 „ .

1-9

11 ,

0-8

11 ,. .

1-8

Noon

7-8

Midnighl

t

1-9

TABLE XVIL
Annual Variation of the Wind in Kingston.

Miles

Miles

per

per

d em.

diem.

January

... 90

July

105

February

... 102

August

91

March

... 113

September .

... 87

April

... 95

October

... 70

May

... 100

November

... 68

Juno

... 125

December

75

Mean : 93 miles per diem.

PUBLICATIONS OF THE INSTITUTE OF JAMAICA.

Objects of the Institute of Jamaica
Root Food Growth in Jamaica
The Timbers of Jamaica ,

Stock and Stock-raising in Jamaica

To he obtained at (he Institute.
... ,., 1881

Rev. J. Radcliffe 6d.
Rev. J. Cork 6d.

Hon. W. B. EsPEDT,

out of print
Archibald Roxburgh,

out of print
D. Morris out of print

»

1887

Cacao : How to Grow and How to Cure It ... 1882

Some Objects of Productive Industry: Native

and other Fibre Plants 1884

Outline of a Lecture on Vegetable Chemistry
The Cultivation of the Orange iu Jamaica

The Vine and its Culture

The Cultivation of the Ramie

On a New Beverage Substance : the Kola Nut ...
The Advantages to result from Railway Extension

On the Geology of Jamaica

On Mining in Jamaica ... ...

The Mineral Springs of Jamaica

The Journal of the Institute of Jamaica {Illustrated) —

Vol. I., Pts. i., ii., iii., iv., vi. (others out of print) per part

Vol. I., bound

Vol. II., Pt. i. (Special Columbus Celebration Double Number)

Vol. II., Pt. ii. (Pt. iii. out of print)

Vol. II., Pt. iv. (Special "Aboriginal Indian Remains" Number) ...
Vol. ll.j -tt. V. ... ... ... ... ... »•• ••• •••

Vol. 11., Pt. VI. ... ... ... ... ... ••• •••

Vol. II., bound ... ...

Classified Book List : Agriculture, 1893

List of Books on Jamaica in the Library of the Institute, Excerpted from the
Catalogue, 1894 ... ... ... ... ••• ••• ••• •••

Bibliotheca Jamaicensis : Some account of the principal works on Jamaica

in the Library of the Institute, 1895
Bibliographia Jamaicensis; a list of Jamaica books and pamphlets, maga-
zine articles, newspapers and maps, most of which are in the Library of
the Institute of Jamaica, 1902

Catalogue of Books in the Library of the Institute, 1895

Jamaica Cartography, 1897 out of print

List of the Decapod Crustacea of Jamaica. By Mary J. Rathbun, 1897 ... Is.

Jamaica in 1901 : A Handbook of Information for Intending Settlers, with

Notes for Visitors. {With illustrations and map) ^d.

The Rainfall Atlas of Jamaica. By Maxwell Hall, M.A., 1892 t2s. Qd,

The Meteorology of Jamaica. By Maxwell Hall, M. A., 1904 Qd.

Bulletin No. 1. A Provisional List of the Fishes of Jamaica. By T. D. A.

Cockerell, F.Z.S., F.E.S., 1892 Gratis

Institute of Jamaica Lectures : Agriculture, 1893 \2s. Qd.

The Economic Geology cf Jamaica. By F. C. Nicholas, 1899 ... ... 2d.

Systematic Catalogue of the Land and Fresh-water Shells of Jamaica. By

Henry Vendryes, 1899

Studies in Jamaica History. By Frank Cundall, F.S.A. Illustrated by

Mrs. Lionel Lee, 1900 2s. 6c?.

D. Morris ^d.

J. J. Bowrey 6c?.

Dr. James Neish 6c?.

Rev. Wm. Griffith 6c?.
Hon. J. C. Phillippo 6c?.

Dr. James Neish 6c?.

Hon. W. B. Espeut 6c?.

^^^^ JRev. H. Scotland 6c?.

1891 Hon. J. C. Phillippo 6c?.

6c?.
7s. 6c?.
2s.
Is.
Is.
Is.
2s.
15s.
Ic?.

3c?.

Qd.

6c?.
2s.

3c?.

t To members of the Institute, Is. 3c?.

Hal

Maxwe

I/The meteorology ot Jamaica

II nil I I

3 5185 00086 6291