A very broad belt of the earth’s surface_Climate and Health in Hot Countries and the Outlines of Tropical Climatology A Popular Treatise on Personal Hygiene in the Hotter Parts of the World, and on the Climates That Will Be Met Within Them.

may be said to possess hot climates; as they include not only those

within the Tropics, but also the sub-tropical zones. Practically

speaking, the whole of Africa, much of South America, the Southern

States of North America with the West Indian Islands, Asia Minor,

Arabia, Persia, India and the Malay Peninsula, the greater part of

China, Australia and the islands lying between it and the continents of

the northern hemisphere, may be said to be included within this general

term. In so wide an area, it is needless to remark that the widest range

of climatic conditions may be found, the only condition common to all

being that of subjection to a fiercer heat than that to which we

Europeans are accustomed, for some or all the months of the year. It

must be remembered, too, that climate is determined not only by the

relation of a place to the parallels of latitude, or to speak more

exactly, to isothermal lines, but is also affected by the elevation of a

site above the sea. Even under a vertical sun, an ascent of 18,000 feet

will land the climber in an absolutely arctic climate, as far as the

temperature of the air is concerned; but it is only in this one item

that we have any similarity to arctic conditions, as the sun’s rays

blaze down even more fiercely than they can at the sea-level, where

they have been tempered by passage through miles of denser air and

watery vapour.

On the crest of the Wakujrui Pass, at 16,500 feet, while the air

temperature at noon stood at 20° below freezing point, the sun

thermometer registered 165°, in May, 1886, when the writer was crossing

the great divide between India and Central Asia; and yet it was

sufficient to remove one’s hat for a minute to realise that to do so

might result in sunstroke. Moreover, apart from the effects of the

rarification of the air on respiration, radiation was so rapid as to be

painfully apparent; one side of the hand turned to the sun would be

scorched, while the other chilled so rapidly that the sensation conveyed

was that of being in contact with a cold liquid; and one was constrained

to wrap up even the face as closely as possible, though the air was

fortunately well-nigh still, whereas cold of similar severity at the

sea-level is quite tolerable as long as there is no wind. Thus, in the

consideration of a given climate, not only geographical position, but

also elevation above the sea must always be taken into account.

To enter into a detailed account of the climatic conditions of the

enormous area under consideration is, of course, out of the question, as

it is a subject on which a special encyclopædia might well be compiled,

so that only the outlines of the subject can be touched upon in the

present short pamphlet. Roughly speaking, we may say that the climates

under consideration have a mean annual temperature at the sea-level of

not less than 64° F. (18° C), while in the equatorial zone it reaches

80° F. (27° C.); but the difference between the maximum and minimum

temperatures in tropical countries is rarely as marked as in

sub-tropical localities, as the range of temperature in the latter is

usually far greater than in the former, so that in spite of the lower

mean, far higher temperatures are recorded for certain regions well

outside the Tropics than can be anywhere found within them. At

Jacobabad, in Upper Sindh, for example, a place some 500 miles outside

the tropical zone, the enormous shade temperature of 127° F. (52·7° C.)

has been registered, and readings of 115° F. (46·1° C.) are quite

common during the hot season over large areas of subtropical India. With

the exception of certain parts of the Soudan, such temperatures are

hardly to be met with in the truly tropical zone, and even these are but

barely within it.

The tropical zone may be defined as that within which the sun is at some

time of the year vertical at noon; or in other words, comprises a belt

extending about 23¹⁄₂° of latitude on either side of the Equator. To the

north and south of it the sun approaches and recedes from the vertical

once during the year, and there are accordingly but two distinct seasons

of summer and winter; but at the Equator the sun necessarily passes

overhead twice during the twelve months, and there are accordingly four

seasons, none of which, however, owing to their shortness, can be very

sharply differentiated from the other. The northern and southern limits

of the Tropics coincide pretty closely with the isotherm, for the

coldest month, of 68° F. (20° C). On the great oceans the coincidence

may be taken as practically absolute, especially along the northern

isotherm, but both isotherms show a tendency to turn towards the Equator

as they approach the western shores of the great continents; so that the

breadth of the tropical belt is considerably contracted in these

positions, and the same remark applies, though to a lesser extent, to

the mean annual isotherm of 68° which bounds the sub-tropical zone. The

tropical zone on the West Coast of America is contracted to little more

than 30° in place of the normal 47°, while as far as mean temperature is

concerned, the temperate zone extends as far north as 20° S. latitude,

well within the geographical Tropics. On the West Coast of Africa the

contraction is equally marked, but mainly at the expense of the northern

isothermal boundary, while the sub-tropical boundaries, on the contrary,

spread out, so as to leave only the extreme northern and southern points

of the continent outside their limits. A third narrowing is to be found

at the western side of the irregular land mass formed by Australia, the

Malay Peninsula, and the intervening islands, but is much less marked,

amounting to a few degrees only. The comparative coolness of the western

sides of the great continental masses is due to the existence of

northerly currents of cold water coming from the frozen seas of the

south pole, which wash the western coasts, while along the east coast

there sets a current of warm water coming from the Equator.

The principal factor in the determination of climatic characteristics is

the fact that while the land heats and cools with great rapidity, the

sea does so more slowly, but holds the heat better. This is due to two

circumstances. In the first place, it requires more heat to warm a given

weight of water than an equivalent mass of the various substances which

constitute the land. In the second place, while both are alike bad

conductors of heat; water, being a fluid, is mobile, and in the colder

parts of the globe where the surface is colder than the intermediate

depths, convection comes into play, apart from which the least movement

at the surface is sufficient to distribute the heat gained from the sun

to a greater depth than is possible in the case of the solid

constituents of the earth’s crust.

The second great determinant of climate is the fact that the temperature

of the air is determined for the most part by that of the surfaces with

which it is brought into contact, rather than by the passage of the

sun’s rays through it, as is well shown in the arctic air temperatures

of great elevations in tropical latitudes. From this it follows that the

atmosphere is mainly heated by the sun’s rays indirectly, from below

where it is in contact with the directly heated, solid and liquid

surface of the globe.

In becoming heated it necessarily expands, and becoming lighter that the

stratum immediately above it, ascends, drawing in, to take its place,

the cooler air that has been in contact with surfaces of air or water

less strongly heated. Now because, as we have seen, water heats and

cools more slowly than land surfaces, along a coast there is always a

tendency to the production of a sea wind from the cooler sea to the

hotter land during the latter part of the day, and inversely of a land

breeze from the more rapidly cooled land to the slowly cooling sea in

the early morning; and in the Tropics, where the sun’s rays are

sufficiently near the vertical to produce a rapid and marked effect,

these diurnal land and sea breezes form a characteristic feature of

littoral climates, and go far to render life tolerable in them. Hence

also it follows that everywhere littoral and marine climates tend to

uniformity, not only as to diurnal but also as to annual variations,

while continental climates tend to wide variations of temperature, and

the seasons differ to a degree never experienced in places on or near

the sea. As an example may be contrasted the climates of Madeira and

Peshawar, in the former of which the difference between the mean

temperatures of the coldest months is under 13° F. (7·2 C), while in the

latter the difference amounts to 40° F. (22·2 C), or three times as

great in the continental climate.

It is further noteworthy that while, in the continental climate, the

hottest and coldest months coincide with the summer and winter

solstices, in the marine climate they lag a month or two after; the

coldest month being February and the hottest August in Madeira, owing to

the slowness with which the water surrounding the island gains and parts

with its heat.

Just as the alternating heat of day and coolness of night produce, in

littoral regions, the daily land and sea breezes, so the greater heating

of the world’s surface over the Tropics produces, throughout the year, a

steady flow of air from the north and south, to take the place of the

air that has become rarified, and so floated to a higher level. These

winds--“the trades”--are not, however, directly from the north and south

respectively, but have also a great deal of easting in their direction,

a circumstance which is explained by the fact that the air, coming as it

does from latitudes where the circumference of the earth is much smaller

than at the Equator, is moving from west to east, only at the

comparatively slower pace of the rest of the earth’s surface at that

latitude; and as they do not at once acquire the quicker motion of the

latitudes to which they have travelled, they lag behind the points of

the earth moving beneath, and so give the effect of an easterly breeze,

just as would be the case with a vehicle driving rapidly eastward

through still air.

Between the two belts influenced by the trade-winds there is naturally a

broad zone, known as “the doldrums,” where the opposing air currents

tend to neutralise each other, and which is naturally characterised by

periods of prolonged calm, alternating with light and variable airs. The

middle line of this zone will obviously be that in which the sun is

vertical at noon, and will consequently lie north or south of the

Equator according to the season of the year. For the typical development

of the “trades” the absolutely uniform surface conditions of the ocean

are indispensable, the variable conditions of soil and vegetation on

land areas impeding their full establishment, by introducing local

variations of capability of heat absorption and radiation; but in spite

of this, though less definite in force and direction, winds of the same

general direction are dominant over the comparatively uniform surface of

the South American continent. When, however, we find a sufficiently

large land area more or less surrounded by sea, the different

heat-absorbing capacity of solid and liquid surfaces may suffice not

merely to neutralise, but to reverse the normal direction of the

tropical and sub-tropical air-currents. Under such conditions, where the

land surface is sufficiently large, the much more rapid heating of the

land surface during summer brings the air in contact with it up to a

much higher temperature than that of the neighbouring seas, and

accordingly over India and Southern China we find that about May or

June, by which month the land has had time to become sufficiently

heated, a strong south-west current--the monsoon[5]--is established,

which, carrying with it air saturated with moisture by its contact with

the sea, determines the rainy season, and by the gradual cooling of the

surface thereby produced, brings about its own termination. In the

winter, on the contrary, over these regions, the prevailing wind resumes

the general direction of the trades.

[5] This is simply a seaman’s corruption of the Arabic word for

season.

Another effect of rapid local heating of the air, the cause of which,

however, is ill understood, is the occurrence of the revolving storms

which are met with during the summer months in low latitudes, and are

generally spoken of as “cyclones” in the Indian Ocean, as typhoons in

the China seas, and as hurricanes in the West Indies. These storms are

determined by the formation of areas of low barometric pressure, to meet

which the air, converging from all sides, takes on a circular motion, or

vortex, round its centre. Nearly all such storms have a double motion,

the vortex itself being not stationary, but travelling over the surface

of the globe in a definite direction. However obscure their origin, the

laws of these storms are now well understood and are as follows: In the

Northern Hemisphere, the vortex revolves in the opposite direction to

that of the hands of a watch, and in the southern in the same direction

as they do; while in both the motion is not truly circular but spiral,

in such manner that a particle carried by the wind, after circling round

the centre several times, ultimately finds itself carried to the centre

of low pressure. In the same way the centre of low pressure, with its

accompanying vortex, always travels at first from east to west, and then

curves away from the Equator, to ultimately take an easterly direction

as it dies out. The dimensions of the vortex, and the area influenced by

such storms, may vary from a few yards to several hundred miles, but in

all cases their force, within the vortex, is very considerable.

Small atmospheric disturbances of this sort, often of no more than 50 or

100 yards in diameter, are very common on the hot, dusty plains of

Rajputana and the Punjab, and are most instructive to watch, as they are

exact reproductions, on a small scale, of the awful visitations that

from time to time devastate huge areas of the earth’s surface.

After a period of exceptional heat and stifling stillness, the still

leaves of the dried-up trees are agitated by light puffs of air of

irregular direction, then away in the east is seen a column of dust, and

this steadily advances till one finds one’s self for a few minutes

buffeted by a violent, fiery wind and choked with dust. When it has

passed and the air has again cleared, this is succeeded by a refreshing

relief of the previously intense heat. When of very small dimensions

these miniature cyclones are locally known as “devils,” and their form,

narrow below and spreading out like a funnel above, can be studied at

leisure. The boundaries of the expanded upper part are indistinct and

fade gradually into the steel-grey of the surrounding glare, but below

the contour of the column is well-nigh as sharp as if it were composed

of solid materials, and may sweep along close by the observer without

involving him.

When of larger dimensions, so that the boundaries of the revolving

column of dust and air are beyond the range of vision, they are known as

“dust storms,” and in spite of the temporary discomforts they cause, are

gladly welcomed, on account of the relief they bring from the

suffocating heat that originated them. When on the larger scale that is

met with in the equatorial zone their violence is well-nigh

incredible--trees are torn up, houses levelled, crops destroyed, and

massive bodies, such, for example, as large anchors lying on the quays

of a dockyard, trundled along as if they were straw hats in an ordinary

gust of wind.

From a sanitary point of view these storms are usually beneficial by

their effect in clearing and cooling the air; but this is unfortunately

only small and temporary, so that they are of little interest to the

hygienist. In any case the prophylaxis against their effects is purely

mechanical, and consists in crawling, if possible, into the nearest cave

or cellar.

Over the great Asiatic continent, especially north of the Himalayas, a

strong northerly current is produced about mid-summer by the area of low

pressure caused by the intense heating of the Siberian steppes, which,

owing to the length of the days at these high latitudes, are exposed to

the sun’s rays for practically the whole twenty-four hours, and the

current thus initiated makes its influence felt for hundreds of miles to

the south of its point of origin, and no doubt reacts upon and modifies

other periodical forces of the same character. A useful law to remember

is that discovered by Professor Buys Ballot, which is to the effect

that, if you stand with your back to the wind, the barometer will be

lower in your left hand than in your right, in the Northern Hemisphere,

and _vice versâ_ south of the Equator.

The effect of ocean currents bringing with them masses of hot or cold

water from other latitudes has already been alluded to, a familiar

example being the mildness of our own climate under the influence of the

Gulf Stream.

In the Southern Hemisphere currents of cold water sweep up from the

Antarctic regions along the western shores of the great masses of land,

counter-currents of warm water flowing down from the Equator along their

eastern sides. In the Northern Hemisphere the reverse is the case, the

cold Arctic currents clinging to the eastern, and the warm equatorial to

the western shores of the continents. The more detailed distribution of

these currents, however, can be better gathered by a little study of the

current chart found in any good atlas, than from any description,

however elaborate.

Climate may also be profoundly modified by the distribution of mountain

chains, the cold summits of which determine the precipitation of the

moisture brought up from the sea, so that while their seaward slopes may

be inordinately rainy, the country beyond may be completely parched; and

apart from such marked contrasts as are produced by the interposition of

great ranges of hills, large differences of rainfall may often be found

in stations a few miles apart. Cherapunji, in Assam, which is said to

hold the world’s record for heavy rainfall, is but 40 miles from

Shillong, the rainfall of which is by no means excessive; and again,

Debunja, in the Cameroons, which is said to hold the second place with a

rainfall of 897 cm., is close to Cameroon, where the rainfall is less

than half that figure.

Another climatic factor of great importance is the amount and character

of the vegetation, for it is a well-ascertained fact that not only does

a heavy rainfall determine luxuriant vegetation, but the converse is

also true, and it is probable that the barrenness of certain regions is

due rather to improvident deforestation than to original natural

dryness. Certain experiments, indeed, go far to show that it is

possible to materially alter the climate of even comparatively small

areas by judicious tree-planting; and it is also certain that the

presence of even small patches of verdure may make a marked difference

in the temperature curves of places within but a few hundred yards of

each other. In the Upper Nile valley, for instance, astounding

differences in the temperature and humidity of the air have been found

to exist in places, respectively barren and cultivated, quite close to

each other, and there is little doubt that local differences of this

sort are worthy of more detailed study than they have as yet received,

and would often be of value in determining the most suitable sites for

habitations and stations.

From a sanitary point of view the variations of the barometer are of

little interest, as at any given level they are never sufficiently great

to have any physiological effect on the human organisation, and hence

the elements of climate that interest us most are temperature and

moisture, for the determination of which all that is required are a

maximum and minimum thermometer, a pair of ordinary wet and dry bulb

instruments and a rain gauge.

In forming an opinion of the characters of any given climate the

temperature of the air is alone of any great importance, the data

afforded by the sun thermometer and that used for determining radiation

being of comparatively little interest, so that the following data are

the most important:--

(1) The mean temperature of each month. This can only be given

accurately by self-registering instruments, but in the absence of these

is usually taken as

max. t. + min. t. + t. at 9 hours + t. at 21 hours

--------------------------------------------------

(2) The mean monthly daily range of temperature, or what is practically

as valuable, the mean maxima and minima.

(3) The “relative humidity” of the air, or the proportion of moisture

actually present to the amount that would suffice to produce saturation,

for each month of the year.

(4) The monthly rainfall.

(5) The number of rainy days in each month.

(6) The average condition of the sky, whether clear or overcast, in each

month.

(7) The amount and daily distribution of wind, its direction being for

us of little moment.

In speaking of air temperatures it must always be understood that

temperatures _in the shade_ are referred to, and in systematic

scientific observations the greatest care must be taken that not only

shall the instruments be thoroughly protected from the direct, but also

from the reflected rays of the sun; and that means are also taken to

secure a free current of air over them.

If an absolutely exact determination of the temperature of the air in

any given situation be required, the observation should be taken by

swinging the instrument, attached to a short cord, rapidly round the

head, and by this method it is possible to secure a close approximation

to the actual air temperature, even in the open and under the direct

rays of the sun.

In considering the effects of climate on human beings it will be well to

commence with a short consideration of the way in which they are

affected by each of these elements of climate.

_Temperature._--In health the temperature of the human blood varies but

little, whatever may be the climatic conditions to which we are

submitted, the normal point being generally taken as 98·4° F. (37° C),

though it may range half a degree or so above or below this level

without prejudice to health or comfort. The mechanism by which this

uniformity of internal temperature is maintained, in spite of the widest

differences in the temperature of our environment, depends upon an

automatic regulation of the nutritive processes going on within the

system.

The various muscular and nervous actions, going on constantly throughout

life, derive the force necessary for their production from the oxidation

of the various articles contained in our food, and as the oxidation of

all its digestible constituents is really nearly as complete as if they

had been subjected to combustion, the body gains nearly as much heat

from the consumption of its food as if the latter were actually burned.

In climates where the temperature of the air is less than that of the

blood, a good deal of heat is conducted away from the body by its

contact with the air; but where, as in hot climates, the difference is

but small, or the temperature of the air may even exceed that of the

blood, it is obvious that some further mechanism is required if the

temperature of the body is to be kept at the normal level of health.

This requirement is met by evaporation from the surface of the body, the

amount of which is regulated automatically by a special set of nerves

which are known as the vaso-motor system, whose function it is to

regulate the calibre of the blood-vessels throughout the body, according

to the varying nutritive necessities of the several organs to which they

are distributed.

We are all familiar with the fact that either extreme heat or violent

exertion will alike bring about free perspiration, and in both cases the

object is the same, viz., to cool down the body which tends to become

overheated; in the one case by the warmth of the surroundings, and in

the other by the activity of the chemical changes going on within the

body to provide the force required for the various muscular and nervous

actions involved in the work performed. On the other hand, under the

influence of cold the skin becomes bloodless and dry, very little blood

being allowed to circulate at the actual surface, the bulk of it being

kept to the deeper parts of the body, well beneath the protective

coating of fat which lies immediately below the skin. Buried in this

fat, and opening by delicate tubes on the surface, are enormous numbers

of small glandular bodies--the sweat-glands--each of which, when

sufficiently freely supplied with blood, pours out a fluid consisting

mainly of water, but containing also a little common salt and minute

quantities of other mineral constituents, as well as a trifling amount

of organic or animal matter, which has served its purpose in the

organism and is thrown off in this way as being of no further value.

In the conversion of water into vapour a large amount of heat is

absorbed, and it is thus equally possible for the body to be kept at a

temperature lower than that of the surrounding air as it is, under more

ordinary conditions, to maintain it at a higher; but the endurance of

intense heat throws an even greater strain on the organism than that of

severe cold, as it cannot be combated in the same way by covering the

body with non-conducting clothing, and under such circumstances

exertion, involving as it does a further production of heat within the

body, becomes well-nigh insupportable. The evil effects of intense heat

become all the more marked in proportion as they are prolonged, and the

effects of air temperatures approaching or exceeding that of the normal

blood continuously, for many days or weeks, without any relief at night,

are most debilitating, and render any considerable amount of muscular

exertion not only painful but dangerous, even to natives of the country,

who, indeed, thoroughly recognise the fact and abstain during such

periods from any laborious tasks not absolutely necessary. The

exhaustion and incapacity produced by extreme heat are naturally

specially marked in persons in whom the sudorific system is ill

developed, and there is no doubt that those who suffer from this defect

in any marked degree should avoid subjecting themselves to such

conditions and be content to remain in more temperate climes. It is

obvious that under such conditions a failure in the action of the sweat

glands must necessarily result in a rise of the body temperature, and

there can be little doubt that this is what takes place in certain cases

of simple “heat apoplexy.” This failure of the sudorific system appears

to be specially favoured by the overcrowding of too many persons within

a limited space. It is only, however, when the temperature stands for

long periods above 90° or 95° F. (33° C.) that these distressing effects

of heat are at all commonly experienced; most Europeans bearing heat up

to this limit even for prolonged periods, if not with comfort, at least

without serious detriment to health, and much higher temperatures are

well borne during the day, provided that the daily range of temperature

is sufficient to secure a definite relief during the night. It will thus

be seen that a wide diurnal range of temperature will go far to

neutralise the bad effects of a high mean temperature, and the

importance of securing information on this point in estimating the

possible effects of a given climate on health is therefore obvious.

The proportion of moisture present in the air has at least as important

a bearing on health as its temperature. It is obvious that when the air

is actually saturated with watery vapour evaporation from the surface of

the body must necessarily be stopped, and with it the natural provision

for preventing an undue rise of the temperature of the body. Actual

saturation combined with high temperature is, however, fortunately rare

for anything but short periods, as the absolute amount of water

requisite to saturation increases rapidly as temperature rises; and

hence warm air, but partially saturated, and therefore still active as

an absorbent of evaporation from moist surfaces, may contain a far

larger absolute amount of water than saturated air at a lower

temperature. In practice, saturated air is only to be found in

situations where it is brought into contact with colder surfaces, such

as that of the earth, cooled by radiation during the night, as is seen

in the production of dew; the dew point being, in fact, the temperature

at which the amount of water present in the air suffices to saturate it.

Apart from its diminution by the formation of dew, the absolute amount

of moisture present in the air, depending as it does on but slowly

changing conditions, can naturally also change but slowly, but the

relative moisture, or the percentage of the amount required to produce

saturation, which is actually present always varies greatly during the

twenty-four hours in all places where the diurnal range of temperature

is at all considerable; so that relative moisture, when given for any

day or other period, always refers to an average. As a rule it is only

the stratum of air of a few yards in thickness that is cooled by contact

with the soil during the night and is hence concerned in the formation

of dew, a fact which is prettily illustrated by the low-lying bands of

vapour which hang over the landscape after a clear night on any fine

morning in the Tropics, and which clear off as if by magic as the

returning sun once more warms up the soil and air. Wherever radiation

is impeded by the shelter of trees, by artificial shelter, or by

sufficiently dense masses of cloud, the temperature of the soil and air

falls but little, and hence, under such circumstances, dew does not

fall.

For practical purposes there are no better hygrometers than those that

depend on the hygroscopic properties of certain organic substances, such

as hair and catgut, and it has been shown by Sresnewsky that the

alteration in length of a hair caused by its absorption of moisture is

directly proportional to the natural logarithm of the degree of relative

humidity, so that such instruments can be graduated for use as

scientific instruments. Rapidity of evaporation is, however,

proportional not to the relative humidity, but to the difference of the

tension of watery vapour present in the air with that of its tension

when saturated--in other words, the difference of tension of watery

vapour at the temperatures of the dry and wet bulb thermometers, a form

of expression which admits of degrees of humidity at different

temperatures to be directly compared. In practice, however, this datum

is rarely to be found in climatic tables, which is of the less

importance, as in its effects on our organisation a difference of 2 or 3

mm. of mercury, from the pressure of saturation at a low temperature,

will give a pleasant sensation of dryness, while at a high temperature

the same deficit of pressure would be felt intolerably close and sultry.

Extreme conditions of either humidity or dryness are, of course, alike

unhealthy, though much of the respiratory irritation ascribed to too dry

air is, I believe, more truly referable to the dust which usually

accompanies such atmospheric conditions; but in any case, there can be

no doubt that alike in hot and cold climates it is far healthier for the

air to be too dry than too moist. With the effects of damp cold we are

all of us only too well acquainted in England, and those who have

experienced the effects of damp heat will never need being reminded of

its debilitating effects. Fortunately, however, relative humidities

exceeding 80 per cent. are but rarely to be found accompanied with

really high air temperatures, and are seldom met with except in

localities blessed with a copious rainfall, which by cooling the air

goes far to render matters tolerable.

The most trying of all climates, however, are those where high

temperatures and relative humidity are combined with an absence of rain,

and under such circumstances a relative humidity of far less than 80 per

cent. gives rise to intolerable closeness and oppression, especially

when combined with stillness of air. Typical examples are the autumnal

climates of the Red Sea and Persian Gulf, the unbearable character of

which is notorious. At Abusher, in the Gulf, for example, in the month

of August rain never falls, there is little or no breeze, and the mean

maximum temperature is 96·5° F. (35·7° C.), while the relative humidity

averages 65 per cent., and though neither figure separately is

remarkably high as compared with what may be met with elsewhere, the

entire combination of conditions is generally admitted to constitute one

of the most unendurable climates in the world. On the other hand, in the

Algerian Sahara in the summer months the relative humidity may fall as

low as 16 per cent., but provided that an unstinted supply of water, to

supply the loss by evaporation, be obtainable, most people find crisp,

dry heat of this sort rather stimulating than otherwise, and even where

the temperature is so high as to become most trying to endurance, the

mortality returns of such situations show that dry heat is really

favourable to health. The reason of this is obviously found in the fact

that a few hours’ exposure to the sun’s rays in such climates suffices

to kill the germs of nearly all specific contagious diseases, and that

the breeding of mosquitoes, which are now known to be the carriers of

several of the most important and deadly of tropical diseases, is

further summarily stopped. A further contributory reason is also found

in the fact, that the population is driven to sleep in the open air

instead of within more or less ill-ventilated houses, and hence obtains

the inestimable benefit of the freest possible ventilation during a

large portion of the twenty-four hours, besides reducing the chances of

the direct infection of the healthy by the sick to a minimum. As a

degree of relative humidity of the air so low as to be in itself

irritating to the respiratory mucous membranes is almost unknown, we may

practically consider that dryness of climate is everywhere synonymous

with healthiness.

_Effects of Amount and Distribution of Rainfall._--As already remarked,

it is quite possible for a climate to be damp and yet have little or no

rainfall, but such instances are rare, and on the other hand, a heavy

rainfall necessarily brings about a coincident increase of relative

humidity. Rain is, moreover, necessarily combined with a cloudy sky,

whereby the heating of the soil during the day and its cooling by

radiation during the night are alike impeded. The immediate effect of a

shower of rain is to cool the air, and this for a double reason: first,

coming as they do from the higher strata of the atmosphere, the

temperature of the raindrops is necessarily much lower than that of the

earth’s surface; and secondly, from the multiplied surfaces of the

descending drops and from the wetted earth there necessarily occurs a

rapid evaporation, whereby a further large amount of heat is absorbed,

but unless showers recur at sufficient intervals to continuously

diminish air temperature, the temporary remission is apt to be dearly

paid for by a period of heat combined with high relative humidity, with

its attendant discomforts of reduced evaporation from the surface of the

body, prickly heat, and the other discomforts inseparable from tropical

damp.

The influence of rainfall on health necessarily depends to a great

extent on the configuration of the land, but assuming that the latter

admits of adequate drainage, more depends upon its distribution than

upon its amount; for the sanitary influences of rain are, in the main,

mechanical, and depend on the “laying” of the dust and the washing away

of infective and otherwise deleterious material. A heavy shower of

sufficient duration will carry away, _viâ_ the river to the sea, the

deleterious products of human occupation during a preceding drought; but

to do this the rain must be heavy while it lasts, for a prolonged

drizzle in a warm climate simply turns the soil into a particularly

efficient cultivation ground for the germs of infective diseases, and

the attendant gloom of the sky stops entirely the beneficent

germ-killing power of the sun’s direct rays. A prolonged drizzle, never

exceeding the absorbtive and drainage capacities of a given site, marks

the maximum of unhealthiness in all climates, and is possibly even more

obnoxious when associated with heat than with cold: so that the most

pleasant tropical climates are those that combine frequent short but

heavy showers with intervals of bright sunlight, a continuously overcast

sky being everywhere unfavourable to health.

To judge, then, the influence of rainfall on health, we require three

data--the total rainfall, the number of rainy days, and the aspect of

the sky in any given season of the year; for the beneficent influence of

light on the animal organisation is at least as marked as it is on

plants, though while the latter fact is a matter of common observation,

the former does not meet with the recognition which it deserves. We

bleach our celery by protecting it from the light, but are apt to forget

that, while the consequent reduction in the amount of its characteristic

essential oil makes its eatable, the plant could hardly survive but for

the application of lime and other artificial antiseptics, which we are

obliged to apply to make up for the lack of the natural protection.

Whether the process of “earthing up” be soothing to a celery plant or

otherwise is a question of which we have no means of judging, but there

can be no doubt that in such matters man is far more practical in the

treatment of plants than of himself, and that in tropical climates he

often suffers by shrinking too much from the immediate effects of the

sun’s rays. In this as in all other affairs, moderation is, of course,

desirable, but the commoner mistake is undoubtedly to shirk too much all

exposure to the sun, whereas those whose avocations take them most into

the open are generally the healthiest in the Tropics as elsewhere.

Contrast the ardent sportsman who spends the broiling days of May and

June in the pursuit of large game, with the lady who spends her days in

a darkened bungalow, and there can be no question as to which suffers

the most from “the effects of climate”; nor is the difference, as is

often suggested, purely one of sex, for it will be noticed that female

medical practitioners and missionaries and other ladies whose

occupations involve their being much in the open are commonly at least

as healthy as men similarly situated.

In all hot countries the period of the rains is the sickly season, but

this is due not so much to any direct evil effects of damp on the human

system as to the fact that the agents and carriers of disease, i.e., low

plant organisms and mosquitoes and other suctorial insects, find in heat

moisture and puddles the conditions that best favour their growth and

multiplication; in other words, the unhealthiness of this season can be

largely obviated by suitable measures of sanitation, so designed as to

impede this growth and multiplication of noxious agencies in the

immediate vicinity of human habitations.

_Effect of Winds on Health._--Save only in so far as it necessarily

raises and transports dust, and that the latter may consist not only of

mineral particles but may contain also deleterious organic matter and

the germs of certain diseases, the action of wind, being equivalent to

so much the freer ventilation, may always be considered desirable in hot

climates. Given a free current of air, the highest air temperatures are

borne with comparative comfort, whereas in stagnant air the sense of

oppression is unbearable. The existence of a steady breeze from a known

direction also makes it possible to artificially cool houses by placing

in the doorway facing the direction of the wind wetted mats, which cool

the air passing through them by the agency of evaporation. It further

makes it possible to live in comfort without the use of punkahs and

other artificial means of keeping up a free current of air; indeed, as a

matter of fact, the habitability of places situated in the Tropics

depends largely on the amount and continuity of the breeze.

As has already been remarked, the amount of dust present in the

atmosphere depends mainly, in the first place, on dryness of the air,

and in the second on the force of wind; but it is also a fact that under

certain conditions, dependent probably on electrical manifestations, a

very still atmosphere may yet carry in suspension a large amount of

dust, and its presence may become inimical to health by causing

irritation to the respiratory organs as well as to the eyes and lining

membrane of the nostrils. This is specially liable to be the case when

the suspended particles are sharp and angular, as in the case of the

micaceous dust, with which, during the dry, hot weather, the air is

often loaded in certain sub-Himalayan stations, producing in many

persons soreness of the eyes and troublesome, dry cough.

Systematic observations on the amount of solid matter suspended in the

air are as yet entirely wanting, but there can be little doubt that they

would, if available, be valuable to the student of public health; for

the high mortality among tradesfolk whose occupations involve the

respiration of a constantly dusty atmosphere is thoroughly well known,

and it is most improbable that what is true of dusty trades is not also

true of dusty places.

Although generally admitted, especially as an article of popular belief,

the influence of the varying electrical states of the atmosphere is as

yet so ill-understood that nothing definite can be stated on the

subject.

SECTION II.

On the Special Characteristics of the Climates of Certain Hot Countries.

There is perhaps no one topic of human conversation that comes in for

more discussion than that of the weather, and yet it is no exaggeration

to say that there is no other as to which exact information is so scanty

or so little accessible, and it is believed that even the following

scanty notes are more complete than can be found in any one work in the

English language.

If the intending emigrant to foreign parts desires to find out something

of the conditions under which he will find himself, he may perhaps,

after much trouble, unearth some undigested data on the subject from the

Agents-General of Colonies, &c.; but he will find it far easier to

ascertain the amount of piece goods bought by the “Borrioula Gah” tribe

than the mean temperature of their capital; and, practically speaking,

the only library containing anything approaching an adequate collection

of the literature of the subject is that of the Royal Meteorological

Society, to whom and to their courteous librarian, Mr. W. Marriott, my

best thanks are due for their ready assistance in the compilation of the

present chapter. Owing to the very varied sources from which the

information has been drawn, any attempt at close uniformity of treatment

is out of the question, but wherever possible the data given comprise

the average mean, mean maximum and mean minimum temperatures, the

rainfall, number of rainy days, and average relative humidity for each

month of the year.

When possible, the figures given are the averages of several years, but

in many cases they refer to a single year only, being derived from

isolated observations or from series which have not as yet been

collated by a meteorological expert. No barometric data have been

included, as they have little interest for any but specialists, and a

study of those given will be found quite sufficient to enable anyone to

judge with what sort of an outfit he should provide himself. It will be,

for example, quite obvious that it is quite useless to take a mackintosh

coat to Wadi Halfa, if anyone will glance at the table given for that

favoured (?) locality. In some cases the maximum and minimum

temperatures tabulated are not the mean, but the absolute maxima and

minima, and therefore represent only exceptional experiences and not

what one may fairly expect. It must be clearly understood, too, that

absolute and mean data are in no sense comparable, as the latter will

always lie several degrees within the former; but in the present state

of meteorological science one has to be thankful for what one can get,

and this, in the case of most of the less advanced countries, is

remarkably little.

The plan of the following notes is to make a sort of climatic tour round

the globe, but it is obvious that it is impossible within the scope of a

work like the present to describe more than a few widely distant

examples, so that it is not even possible to include all our tropical

colonies; but it is hoped that those given will suffice to give a

general idea of what may be expected in most parts of the world. With

few exceptions all data are given both in the English and in the metric

systems.

_THE MEDITERRANEAN BASIN._--None of the countries comprising the

European shores of this basin can be said to come well under the heading

of “hot countries,” and those on the African shore are of interest

rather as winter health resorts than as tropical places of residence.

The first of these that requires notice is--

_Algeria._--Situated in lat. 37° N., within a couple of days’ steaming

from Marseilles, this pleasant French colony is much the most easily

accessible sub-tropical health station for the whole of western Europe,

and forms an excellent resort for persons who find themselves unable to

withstand the rigours of a northern winter. Thanks to the French talent

in municipal organisation, the traveller finds himself at once among the

novel sights and sounds of civilisation of the Oriental type, and yet

surrounded with all the comforts and amenities of a fine European town.

Few health-seekers venture far from the coast, though there must be many

places in the interior that would be well suited for early cases of

consumption, as the air of the coast is perhaps too “relaxing” for some

cases of the sort. For the north coast of Africa, the rainfall is

considerable, but in spite of this, on the average, the air is generally

dry, as evidenced by the low average relative humidity.

The country may be divided into four zones, which present great

differences of climate.

(1) A narrow littoral zone of low ground, often only a few miles wide.

Most of the ports face eastward and are well sheltered by the

neighbouring hills.

(2) The Tel, composed of plains and elevated mountain masses cut up by

deep valleys, at the bottom of which are torrents which are dry for the

greater part of the year.

(3) A high plateau of triangular form about 140 miles wide; intensely

dry, but with scattered salt marshes which dry up during the summer.

(4) The Sahara, an immense sandy basin absolutely devoid of

water-courses except quite to the north.

The following table of mean temperatures will give some idea of the

degree of heat that is met with throughout the year in these different

regions:--

MONTHLY MEAN TEMPERATURE OF ALGERIAN STATIONS SITUATED IN THE FOUR

ABOVE-MENTIONED ZONES.

======================+=====+=====+===========+===========+===========

| | |----+------+----+------+----+------

| | | F. | ~C.~ | F. | ~C.~ | F. | ~C.~

----------------------+-----+-----+----+------+----+------+----+------

Algiers (on the coast)| 68| 22|53·8|~12·1~|54·6|~12·6~|57·0|~13·9~

Orleansville (on the | 390| 119|48·3| ~9·1~|50·2|~10·1~|54·2|~12·3~

Térriet el Haad (on |3,700|1,125|41·0| ~5·0~|43·0| ~6·1~|47·5| ~8·6~

Géryville (on the high|4,300|1,310|37·5| ~3·1~|40·2| ~4·5~|45·5| ~7·5~

Biskra (Sahara) | 410| 125|50·2|~10·1~|54·3|~12·4~|57·0|~13·9~

======================+=====+=====+====+======+====+======+====+======

======================+===========+===========+===========+===========

Station | April | May | June | July

|----+------+----+------+----+------+----+------

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | F. | ~C.~

----------------------+----+------+----+------+----+------+----+------

Algiers (on the coast)|61·4|~16·3~|66·1|~19·0~|72·2|~22·3~|76·0|~24·4~

Orleansville (on the |61·7|~16·3~|68·4|~20·2~|77·9|~25·5~|85·0|~29·4~

Térriet el Haad (on |52·3|~11·2~|59·6|~15·4~|69·8|~21·0~|77·4|~25·2~

Géryville (on the high|52·8|~11·6~|63·8|~17·7~|74·0|~22·2~|79·7|~26·5~

Biskra (Sahara) |66·0|~18·9~|76·0|~24·4~|84·4|~29·1~|90·0|~32·2~

======================+====+======+====+======+====+======+====+======

======================+===========+===========+===========+===========

Station | August | September | October | November

|----+------+----+------+----+------+----+------

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | F. | ~C.~

----------------------+----+------+----+------+----+------+----+------

Algiers (on the coast)|77·0|~25·0~|74·2|~23·4~|67·5|~19·7~|60·5|~15·8~

Orleansville (on the |85·7|~29·8~|77·2|~25·1~|66·7|~19·3~|56·7|~13·7~

Térriet el Haad (on |78·7|~25·9~|68·0|~20·0~|58·3|~14·6~|49·9| ~9·9~

Géryville (on the high|79·7|~26·5~|68·5|~20·3~|56·7|~13·7~|46·5| ~8·1~

Biskra (Sahara) |90·0|~32·2~|80·2|~26·8~|68·0|~20·0~|57·7|~14·3~

======================+====+======+====+======+====+======+====+======

======================+===========+===========

Station | December | Year

|----+------+----+------

| F. | ~C.~ | F. | ~C.~

----------------------+----+------+----+------

Algiers (on the coast)|54·9|~12·7~|64·5|~18·1~

Orleansville (on the |49·9| ~9·9~|65·2|~18·4~

low “Tel”) | | | |

Térriet el Haad (on |43·5| ~6·4~|57·3|~14·1~

the high “Tel”) | | | |

Géryville (on the high|39·8| ~4·3~|56·7|~13·7~

plateau) | | | |

Biskra (Sahara) |51·5|~10·8~|68·5|~20·3~

======================+====+======+====+======

NOTE.--In this and all following tables, F. stands for degrees

Fahrenheit; C. for degrees Centigrade; E.F., elevation above the sea

in feet; E.M., the same expressed in metres; Ins., inches, English;

Mm., millimetres.

The character of the climate of the capital, which may be considered

typical of the coast health resorts, may be gathered from the following

table:--

ALGIERS. LAT. 33° 47′ N.; LONG. 0° 44′ E. E.F. 105; E.M. 33·5.

========+===========+===========+===========+=====+=============+=====

| |Temperature|Temperature| Hu- | | of

+----+------+----+------+----+------+midi-+-----+-------+Rainy

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | ty | Ins.| ~Mm.~ | Days

--------+----+------+----+------+----+------+-----+-----+-------+-----

January |56·0|~13·3~|62·7|~17·0~|50·2|~10·1~| 60 | 3·25| ~82·5~| 16

February|61·3|~16·3~|70·2|~21·2~|54·8|~12·7~| 61 | 3·17| ~80·6~| 9

March |57·2|~14·0~|64·5|~18·1~|51·5|~10·8~| 62 | 3·14| ~79·1~| 15

April |60·5|~15·8~|67·8|~19·9~|54·2|~12·3~| 65 | 3·46| ~88·4~| 10

May |66·7|~19·3~|74·7|~23·7~|60·2|~15·7~| 62 | 3·53| ~89·2~| 6

June |72·5|~22·5~|79·7|~26·5~|66·7|~19·3~| 71 | 0·75| ~19·1~| 6

July |75·8|~24·1~|83·0|~28·3~|68·5|~20·3~| 68 | 0·70| ~17·2~| 2

August |77·0|~25·0~|84·3|~29·1~|70·0|~21·1~| 67 | 0·20| ~4·9~| 4

ber |75·5|~24·2~|83·2|~28·4~|70·3|~21·3~| 73 | 0·28| ~7·1~| 9

October |71·2|~21·8~|79·2|~26·2~|66·0|~18·9~| 72 | 1·52| ~38·6~| 11

November|59·8|~15·5~|67·3|~19·6~|55·7|~13·2~| 70 | 9·0 |~228·3~| 22

December|56·8|~13·8~|67·5|~19·7~|51·7|~10·9~| 69 | 1·65| ~42·0~| 7

--------+----+------+----+------+----+------+-----+-----+-------+-----

Year |65·8|~18·8~|73·2|~22·9~|59·8|~15·5~| 66·7|30·5 |~777·0~| 117

========+====+======+====+======+====+======+=====+=====+=======+=====

From this it may be seen that Algiers possesses a very desirable climate

all the year round, though a trifle too rainy in late autumn.

The figures are those of the year 1901, as the French Government does

not appear to have furnished the library with mean normal results.

_Malta._--Owing to the large number of our officers and men serving

there, the climate of this small island, which is delightful during the

winter, is of interest to many, but it perhaps barely merits the name of

a hot climate. While resembling in some respects the climate of southern

Italy, it approximates more closely to that of northern Africa, the

rainfall being very scanty.

The following are the principal climatic data:--

VALETTA. LAT. 35° 54′ N.; LONG. 14° 30′ E.; NEAR SEA LEVEL.

=========+===========+===========+=====+=============+==============

+----+------+----+------+ mid +-----+-------+

| F. | ~C.~ | F. | ~C.~ | ity | Ins.| ~Mm.~ |

---------+----+------+----+------+-----+-----+-------+--------------

January |60·2|~15·7~|50·1|~10·0~| 78 | 5·51|~139·7~|Total Annual

February |63·0|~17·2~|50·3|~10·2~| 79 | 1·04| ~26·2~|Rainfall, 17·1

March |63·4|~16·8~|49·8|~9·9~ | 73 | 1·04| ~26·2~|ins., or 40·3

April |65·6|~18·5~|52·4|~11·3~| 78 | 2·18| ~55·2~|cm.

May |72·3|~22·4~|59·1|~15·0~| 78 | 0·55| ~14·0~|

June |80·7|~27·0~|64·9|~18·3~| 72 | 0·38| ~10·0~|

July |88·0|~31·1~|70·6|~21·3~| 70 | 0·00| ~0·0~|

August |84·9|~29·4~|70·7|~21·4~| 77 | 0·02| ~0·1~|

September|83·3|~28·5~|68·7|~20·4~| 77 | 0·10| ~2·5~|

October |81·7|~27·5~|67·3|~19·8~| 78 | 0·60| ~15·2~|

November |71·1|~21·7~|59·0|~15·0~| 83 | 3·64| ~92·5~|

December |62·6|~16·8~|52·2|~11·2~| 85 | 1·04| ~26·2~|

=========+====+======+====+======+=====+=====+=======+==============

During the summer, periods of hot dry winds blowing from the burning

African deserts are somewhat trying, but these do not, as a rule, last

for many consecutive days, and on the whole the climate is not

unhealthy.

A peculiar infective fever, commonly known as “Malta fever,” but also

met with in other parts of the Mediterranean littoral, as well as in

India, and very troublesome on account of its obstinate tendency to

relapse, is the most serious drawback in the matter of disease, but

under improving modern sanitation the disease is yearly becoming less

common.

The climate of the Syrian coast is very similar, but somewhat warmer,

with a heavier rainfall; so also is that of Algiers and the North

African coast generally, there being, however, mostly a wider range

between the hottest and coldest months than in the purely insular Malta.

Malaria, dysentery, and other tropical diseases are not uncommon, but

seldom either widely spread or particularly virulent. As we leave the

coast, the range of temperature, both annual and diurnal, rapidly

increases, and is especially marked in the highlands of Asia Minor, as,

for example, at Erzerum, where the temperature in January falls as low

as -20° F. (-29° C.), and in summer may exceed 90° F. (31° C.).

_Cyprus._--Long. 32° 20′ to 34° 35′ E; lat. 34° 33′ to 35° 41′ N. Our

administrative connection with this island, and the circumstance that it

has of late been strongly recommended as a fairly stimulating winter

health resort for delicate people, and especially for cases of chest

diseases and others, make it desirable to include an account of it

within our list.

The following are the principal climatic data:--

NIKOSIA, ON CENTRAL PLAIN.

=========+============+===========+======+===========+======

| | | ity | |Days

+-----+------+----+------+------+-----+-----+

| F. | ~C.~ | F. | ~C.~ | % | Ins.|~Mm.~|

---------+-----+------+----+------+------+-----+-----+------

January | 73·4|~23·0~|32·3| ~0·2~| 84 | 4·0 |~101~| 11·8

February | 70·7|~21·5~|31·8| ~0·1~| 84 | 3·70| ~94~| 11·8

March | 76·5|~24·7~|36·4| ~2·4~| 81 | 1·23| ~31~| 7·4

April | 84·5|~29·2~|38·8| ~3·8~| 78 | 1·14| ~29~| 4·5

May | 90·4|~32·4~|46·2| ~7·9~| 74 | 0·63| ~16~| 4·3

June |100·0|~37·8~|52·4|~11·3~| 67 | 0·39| ~10~| 1·4

July |100·7|~38·3~|55·5|~13·1~| 68 | 0·13| ~3~| 0·3

August |103·0|~39·4~|57·2|~14·0~| 66 | 0·8 | ~20~| 0·5

September|100·5|~38·1~|54·4|~12·3~| 73 | 0·04| ~1~| 0·6

October | 93·5|~34·2~|47·7| ~8·7~| 76 | 0·36| ~9~| 2·3

November | 84·5|~29·0~|39·3| ~4·1~| 82 | 1·97| ~50~| 6·5

December | 77·5|~25·3~|34·0| ~1·1~| 85 | 2·31| ~59~| 7·8

=========+=====+======+====+======+======+=====+=====+======

The climate is somewhat cooler in summer on the coast, and the rainfall

slightly higher, but with a smaller number of rainy days.

The island is mountainous; a great mass of hills occupying the greater

part of the southern half, and reaching an elevation of over 6,400 feet

at Mount Troödos, where a summer sanatorium has been established. A

lower range of hills fringes the entire northern shore, and between the

two is a central plain, on the highest part of which, at an elevation of

about 500 feet, is situated the capital, Nikosia. These hills shelter

the central plain from the bitter winds of the Taurus range in Asia

Minor during winter, but, on the other hand, cut off the cooling

sea-breezes in summer. For eight months in the year the rainfall is

inappreciable, and the summer appearance of the plains arid in the

extreme, but the advent of the winter rains in October changes the scene

to one of the greatest fertility. The hill country, on the other hand,

is generally well-clothed with pine-forests, and enjoys, during the

summer, a very pleasant climate. At Nikosia the mean temperature of the

year is 67·2°, the extreme maximum being 108°, and the minimum 28°,

showing the large range of 80°.

At the hill station on Mount Troödos, at an elevation of 5,000 feet, the

excessive heat of the plains is entirely avoided. The season there opens

in June and closes in October, the temperature never exceeding 85° F. in

1901. The following table shows the great gain in coolness:--

MEAN TEMPERATURES, FAHRENHEIT.

1901 Nikosia Troödos Difference

June 77·2° 61·7° 15·5°

July 83·7° 71·7° 12·0°

August 83·3° 68·2° 15·1°

September 78·8° 61·6° 17·2°

During the greater part of the year the wind is usually from the

north-west, but during the coldest part of the winter is usually from

the east. It will be noticed that the general characters of the climate

are rather those of a Continental than of an insular situation. The air

is almost always highly charged with electricity, and there is

comparatively little malaria or other specially tropical diseases.

_Egypt._--The climate of this country is, even from the

all-the-year-round point of view, one of the finest in the world, and

hence its well-deserved popularity as a winter health resort. Apart from

the “Khamseen,” which those used to Indian hot weather might esteem a

change for the better, its one drawback is what may be termed the

co-efficient of rapacity of its hotel-keepers; as for the casual

visitor, it is certainly an expensive country.

With endless sights of antiquarian interest, and a gay cosmopolitan

society, there is little chance of boredom for either the studious or

frivolous, and with the possible exception of California, no climate

affords a better combination of warmth and sunlight, with a clean,

stimulating atmosphere. It owes this to its peculiar geographical

characters, for although it includes on the map a large area, the

actually inhabited portion consists of only a narrow strip, a few miles

wide, on either side of the Nile; as all the land beyond the reach of

the annual overflow of the river, which is at its maximum in September,

and lowest in June, is absolute desert, the intense dryness of which is

necessarily fatal to all forms of vegetable life, including the organic

germs of disease. On this account, even in the middle of the cultivated

strip, the air has never been fouled by passing over any considerable

extent of habitations and cultivation, with their inevitable emanations,

but must always come, almost fresh and germ-free, from the illimitable

expanse of sand and rock that immediately succeeds the narrow band of

river alluvium.

Dr. Dalrymple, one of the earliest writers on the subject, remarks, “It

is scarcely possible to imagine anything more invigorating and

life-giving than the air of the desert; there is a dryness and

elasticity about it like nothing else, and the sense of renovation when

breathing it is, to the languid invalid, like a new lease of life.”

Both he and Dr. Sandwith, from whose excellent “Egypt as a Winter

Resort” the following tables are taken, seem agreed as to its

suitability for all cases of chest disease that have not gone too far to

be amendable to climatic treatment of any sort, and Dr. Sandwith finds

it also suitable for such cases of heart and kidney affections as are

unfavourably affected by cold; while the sulphur baths of Helouan have

been found remarkably useful in the chronic forms of rheumatoid

arthritis, rheumatism and gout.

The main characteristic of the climate is its intense dryness. Even on

the coast at Alexandria, the rainfall is but trifling, and above Cairo

it may almost be neglected; but in spite of this even during the hottest

months the climate is quite bearable. “Northern rooms, if closed in good

time, need never exceed 83° in the hot weather, or fall below 52° in the

cold season, provided the sun-warmed air be allowed free entry.” The

prevailing wind is a gentle breeze from the north, but both at Cairo and

Alexandria, during the fifty days about Easter-time, a peculiar

dust-laden wind, highly charged with electricity, and known as “the

Khamseen,” blows at intervals. It is very disagreeable while it lasts,

the dust sometimes obscuring the sun almost as completely as a London

fog, but it rarely persists more than two days at a time, and does not

usually occur more than three or four times in a season. The following

tables will give a good general idea of the climate:--

ALEXANDRIA. LAT. 31° 13′ N.; LONG. 26° 53′ E. E.F., 66 ft.

=========+==================+======+======+=======+=============

+----+------+------+ tive | in | 0-10 +------+------

| | ma | ma | % | | | |

---------+----+------+------+------+------+-------+------+------

January |58·1| 64·0 | 53·2 | 67 | 2·33 | 4 | N. | 2·5

February |58·6| 64·2 | 54·0 | 65 | 1·43 | 4 | N.W. | 2·5

March |61·6| 68·0 | 56·0 | 65 | ·78 | 3 | N.W. | 2·7

April |66·0| 73·0 | 60·6 | 66 | ·12 | 2 | N. | 2·5

May |70·0| 75·4 | 65·6 | 70 | ·03 | 2 | N. | 2·2

June |75·0| 79·6 | 71·2 | 72 | -- | 1 | N. | 2·3

July |77·6| 81·2 | 74·8 | 75 | -- | 1 |N.N.W.| 2·4

August |79·0| 82·4 | 76·1 | 73 | -- | 1 | N. | 2·0

September|77·4| 81·2 | 74·3 | 69 | ·11 | 2 | N. | 2·3

October |74·6| 79·2 | 70·6 | 68 | ·33 | 2 | N. | 2·1

November |68·2| 73·4 | 64·0 | 67 | 1·32 | 3 | N. | 2·2

December |62·0| 67·8 | 57·0 | 67 | 1·79 | 4 | N. | 2·4

---------+----+------+------+------+------+-------+------+------

Annual |69·0| 74·1 | 64·8 | 68·6 | 8·24 | 2·4 | N. | 2·3

=========+====+======+======+======+======+=======+======+======

CAIRO. LAT. 30° 4′ N.; LONG. 31° 15′ E. E.F., 108.

=========+==================+======+======+=======+=============

+----+------+------+ tive | in | 0-10 +------+------

| | ma | ma | % | | | |

---------+----+------+------+------+------+-------+------+------

January |53·6| 61·4 | 46·6 | 69·7 | ·19 | 4·1 | S.W. | 2·2

February |57·0| 65·3 | 48·8 | 66·2 | ·24 | 4·2 | N. | 1·4

March |62·8| 73·2 | 53·0 | 56·2 | ·03 | 3·4 | N. | 2·5

April |70·4| 81·2 | 59·9 | 47·8 | ·12 | 3·4 | N. | 2·6

May |75·2| 86·8 | 63·4 | 48·4 | ·22 | 2·3 | N. | 2·8

June |82·6| 94·7 | 70·2 | 44·0 | ·02 | 1·0 | N. | 3·0

July |83·8| 93·0 | 72·2 | 49·0 | -- | 1·2 | N. | 4·3

August |82·2| 92·9 | 71·4 | 55·3 | -- | 1·6 | N. | 4·1

September|77·8| 87·5 | 68·0 | 62·1 | -- | 1·8 | N. | 4·3

October |74·3| 84·0 | 64·8 | 65·8 | -- | 2·5 | N. | 3·2

November |64·4| 74·2 | 56·3 | 67·5 | ·21 | 3·0 | N. | 2·1

December |58·4| 67·7 | 50·4 | 69·6 | ·19 | 3·7 | N. | 2·2

---------+----+------+------+------+------+-------+------+--------

Year |70·2| 80·1 | 60·4 | 58·46| 1·22 | 2·6 | N. | 2·9

=========+====+======+======+======+======+=======+======+========

LUXOR. LAT. 25° 40′ N.; LONG. 32° 35′ E. E.F., 292.

Winter Climate.

=========+==================+======+======+=======+=============

+----+------+------+ tive | in | 0-10 +------+------

| | ma | ma | % | | | |

---------+----+------+------+------+------+-------+------+------

November | -- | 78·99| 62·1 | -- | | -- | S.W.| 1·0

December | -- | 70·0 | 53·6 | -- | _N | -- | N.E.| 1·8

January |56·7| 65·1 | 41·3 | 53·2 | i | 2·9 | N.W.| 1·0

February |62·6| 70·6 | 42·4 | 51·0 | l | 1·9 | N.W.| 1·1

March |66·9| 80·1 | 47·6 | 45·0 | ._ | 2·1 | {N.W.|} 0·7

| | | | | | | {N.E.|}

=========+====+======+======+======+======+=======+======+======

_Assouan_, 133 miles further up the Nile, has a winter climate which is

said to be almost 5° F. higher than Luxor, and to be freer from

dust-storms. The building of the great dam and the large artificial lake

which has been thus formed can hardly fail to modify the climate, so

that it is hardly worth while reproducing Dr. Sandwith’s table.

For the rest, the whole of Egypt up to this latitude may be said to be

very healthy for Europeans, there being much less malaria than one would

be inclined to expect as a consequence of the annual overflowing of the

Nile; a circumstance which may, I believe, be attributed to the

generally neat character of the cultivation, and the care with which

every square yard of cultivable soil is utilised. Internal worms are,

however, extremely common amongst the natives, but care in the matter of

drinking water will render the risk run by the European very trifling.

Another terribly common disease amongst the natives is granular

ophthalmia, a disease easily acquired by contact, or indirectly through

the agency of flies, but Dr. Sandwith finds that it is extremely rarely

taken by Europeans, though soreness of the eyes from dust and glare is

not uncommon, for which he recommends the daily use of a little boracic

solution as a toilet wash. It might, however, be perhaps advisable to

protect young children by means of a veil when abroad, especially when

entrusted to the care of a native attendant.

_THE REMAINDER OF THE AFRICAN CONTINENT._--Our knowledge of African

meteorology is necessarily in its infancy, and it is only possible to

furnish a few tables of widely distant parts of this immense area, which

may give some idea of its climatic characters. The whole of the northern

part of the continent is extremely dry, much of it being quite rainless,

especially towards its eastern side. Following on this is the equatorial

belt, a great portion of which is barely, if at all, explored, but which

seems to usually present the general characters of such latitudes and to

be usually blessed with an ample rainfall across the entire width of the

continent. Southward of the equatorial zone we again meet with immense

dry and desert areas, such as the Karoo, but here it is the western side

that is the more arid, none of the south-eastern coast being in any

sense rainless.

Malaria is extremely rife in almost all parts of the huge peninsula, and

in addition to this we have in “Blackwater fever” and sleeping sickness,

diseases which seem to be at present its own peculiar privilege, though,

fortunately, yellow fever is not as yet included in its list of dangers.

The low-lying country along the coast and of the great rivers is

notoriously unhealthy, such as the Bight of Benin, where, according to

the sailor’s proverb,

“There’s two comes out

Where three goes in.”

But inland there are considerable tracts of elevated country which

present climates by no means to be despised, and which will no doubt in

time, with the advance of civilisation, become eligible and healthy

sites for European occupation, and more than one example of climatic

conditions that appear decidedly inviting will be found amongst the

tables furnished below.

An example of the climate of the Sahara has already been furnished in

the notice of Algeria, and in the northern part of the continent the

only other at all well-known climate (apart from Egypt) is the _Soudan_.

Practically rainless in parts, the climate is intensely hot and dry, the

relative humidity showing one of the lowest records in our collection;

but as the equatorial zone is approached a moderate rainfall develops,

and throughout the region the large daily range of temperature results

in the nights being comparatively cool, and therefore less trying than

many parts of India. The northern portion is too dry to be very

unhealthy, apart from the danger of abdominal chills, but as we ascend

the Nile it expands into the immense marshes described by Baker and

others, which are necessarily intensely malarious, while round the great

lakes the sleeping sickness, previously rare or unknown there, is

spreading rapidly.

Commencing with the dry Soudanese region, climatic tables of three

stations will be found below, the first and most northern of which, it

will be seen, is practically rainless. The figures of the first table

are averages of ten years’ observations.

WADI HALFA. LAT. 21° 55′ N.; LONG. 31° 19′ E. E.F., 590; E.M., 128.

=========+===========+============+===========+===========+===========

+----+------+-----+------+----+------+-----+-----+

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | At | At |

| | | | | | | 9 h.|21 h.|

---------+----+------+-----+------+----+------+-----+-----+-----------

January |59·4|~15·2~|73.7 |~23·2~|47·5| ~8·6~| 42 | 44 |

February |62·6|~17·0~| 77·2|~25·1~|48·4| ~9·1~| 39 | 36 |

March |71·5|~21·9~| 87·5|~30·8~|56·5|~13·6~| 30 | 30 |

April |80·5|~26·9~| 95·8|~35·5~|63·7|~17·6~| 23 | 24 |

May |87·8|~31·0~|104·3|~40·2~|70·5|~21·4~| 17 | 19 |Practically

June |90·7|~32·6~|106·7|~41·6~|74·4|~23·5~| 20 | 22 |_nil_.

July |90·5|~32·5~|105·7|~40·9~|74·5|~23·6~| 23 | 30 |Drops

August |90·0|~32·2~|103·5|~39·7~|75·0|~23·9~| 31 | 34 |recorded

September|88·7|~31·4~| 99·6|~37·6~|73·5|~23·1~| 35 | 38 |15 times

October |82·5|~28·1~| 97·2|~36·2~|69·0|~20·6~| 37 | 10 |in 10 years

November |70·7|~21·8~| 85·0|~29·4~|58·7|~14·8~| 41 | 43 |

December |63·0|~17·2~| 76·6|~24·7~|51·0|~10·6~| 45 | 45 |

---------+----+------+-----+------+----+------+-----+-----+

Year |78·0|~25·6~| 92·9|~33·8~|63·5|~17·8~| -- | -- |

=========+====+======+=====+======+====+======+=====+=====+===========

The two remaining tables are for the year 1901, and are not even

complete in places. Kassala is, of course, much nearer the sea than

Omdurman, and hence its better rainfall.

OMDURMAN. LAT. 15° 38′; LONG. 32° 29′. E.F., 1,250; E.M., 376.

=========+===========+============+===========+======+============

+----+------+-----+------+----+------+ ity +----+-------

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | |Ins.| ~Mm.~

---------+----+------+-----+------+----+------+------+----+-------

January |72·9|~22·7~| 88·5|~31·4~|62·6|~17·0~| 24 | -- | --

February |79·9|~26·3~| 94·5|~34·7~|70·2|~21·2~| 28 | -- | --

March |82·7|~28·2~| 99·7|~37·6~| -- | -- | 19 | -- | --

April |87·5|~30·8~|103·7|~39·8~|72·5|~22·5~| 14 | -- | --

May |93·0|~33·9~|112·0|~42·4~|79·0|~26·1~| 20 | -- | --

June |89·9|~32·1~|106·2|~41·2~|77·4|~25·2~| 46 |0·63| ~16·1~

July |90·4|~32·4~|103·9|~39·9~|79·3|~26·3~| 48 |0·50| ~12·8~

August |87·0|~30·6~| 99·0|~37·2~|77·7|~25·5~| 58 |0·13| ~3·3~

September|90·4|~32·4~|104·5|~40·3~|81·0|~27·2~| 40 | -- | --

October |89·9|~32·1~|103·2|~39·5~|79·5|~26·4~| 30 |0·32| ~8·0~

November |82·4|~28·0~| 96·7|~35·9~|72·4|~22·4~| 24 | -- | --

December |76·2|~24·5~| 91·2|~32·9~|65·5|~18·6~| 28 | -- | --

---------+----+------+-----+------+----+------+------+----+-------

Year |85·2|~29·5~| 99·9|~37·7~|74·4|~23·5~| 32 |1·58| ~40·2~

=========+====+======+=====+======+====+======+======+====+=======

KASSALA. LAT. 15° 28′ N.; LONG. 36° 24′ E.

=========+===========+============+===========+======+===========

+----+------+-----+------+----+------+ ity +----+-------

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | |Ins.| ~Mm.~

---------+----+------+-----+------+----+------+------+----+-------

January |72·6|~22·6~| 86·4|~30·2~|58·9|~14·9~| -- | Drops

February | -- | -- | 95·6|~35·4~| -- | -- | -- | -- | --

March |82·0|~27·8~|100·5|~38·1~|68·1|~20·1~| 51 | -- | --

April |86·4|~30·2~|103·3|~39·6~|73·0|~22·8~| 32 |0·08| ~2·0~

May |89·6|~32·0~|106·2|~41·2~|76·9|~24·9~| 25 |0·25| ~6·4~

June |86·0|~30·0~|101·2|~38·4~|75·5|~24·2~| 40 |2·85| ~72·4~

July |83·7|~28·7~| 96·9|~36·0~|74·2|~23·4~| 59 |1·48| ~37·4~

August |79·8|~26·6~| 92·5|~33·6~|81·8|~27·7~| 64 |3·96|~100·6~

September| -- | -- | 99·8|~37·7~|75·4|~24·1~| -- |1·24| ~31·3~

October | -- | -- |101·4|~38·5~|76·5|~24·7~| -- | -- | --

November | -- | -- | 99·2|~37·3~|73·5|~23·1~| -- | -- | --

December | -- | -- | -- | -- | -- | -- | -- | -- | --

---------+----+------+-----+------+----+------+------+----+-------

Year |83·0|~28·3~| 98·5|~36·9~| -- | -- | 40 |9·84|~250·1~

=========+====+======+=====+======+====+======+======+====+=======

_Abyssinia._--The greater part of the Ethiopian empire is high ground,

and in many parts of the country the climate may almost be described as

temperate, as may be judged from the following statement (derived from a

French official source) of the climatic factors of the capital during

the year 1901.

ADIS-ABABA. LAT. 9° 1′ N.; LONG. 38° 43′ E. E.F., ABOUT 7,000.

========+====+======+===========+===========+=====+==============+=====

| |Temperature|Temperature| Hu- | | of

+----+------+----+------+----+------+midi-+-----+--------+Rainy

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | ty | Ins.| ~Mm.~ | Days

--------+----+------+----+------+----+------+-----+-----+--------+-----

January | -- | -- | -- | -- | -- | -- | -- | -- | -- | --

February|55·4|~18·0~|73·4|~23·0~|47·9| ~8·8~| 81 | 2·15| ~54·6~| 8

March |58·0|~14·4~|75·7|~24·3~|50·4|~10·2~| 83 | 5·23| ~132·7~| 10

April |58·4|~14·6~|74·2|~23·3~|51·4|~10·7~| 86 | 4·39| ~111·1~| 11

May |60·9|~16·0~|78·5|~25·8~|52·7|~11·5~| 74 | 1·36| ~34·7~| 4

June |57·5|~14·2~|72·3|~22·4~|49·7| ~9·8~| 72 | 8·36| ~212·3~| 30

July |56·0|~13·3~|69·0|~20·6~|49·7| ~9·8~| 80 |10·10| ~256·5~| 30

August |60·2|~15·7~|69·0|~20·6~|50·0|~10·0~| 79 | 9·46| ~240·1~| 28

ber |63·0|~17·2~|73·5|~23·1~|49·8| ~9·9~| 66 | 5·48| ~139·2~| 14

October |61·5|~16·4~|77·2|~25·1~|46·5| ~8·1~| 37 | 0·60| ~15·2~| 3

November|60·0|~15·6~|77·0|~25·0~|44·5| ~6·9~| 28 | -- | -- | --

December|57·2|~14·0~|74·4|~23·5~|44·3| ~6·7~| 39 | 0·54| ~13·5~| 3

--------+----+------+----+------+----+------+-----+-----+--------+-----

Year |58·4|~14·6~|72·2|~23·6~|48·7| ~9·3~| 66 |49·11|~1247·5~| 141

========+====+======+====+======+====+======+=====+=====+========+=====

_The Region of the Great Lakes._--Turning now to the great lakes of

Central Africa, the following data from Hann’s “Klimatologie” may give

some notion of the conditions prevailing.

In the Victoria Nyanza region (at E.F., 3,900; E.M., 1,200), according

to E. G. Rauenstein, the mean annual temperature is 71·2° F. (21·8° C.),

March 73·7° F. (23·2° C.), July 67·7° F. (19·8° C.), October 75·2° F.

(24·0° C.), December 71·7° F. (22·0° C.). The extreme mean monthly

maxima and minima (of January and February), 94° to 54° F. (34·4° to

12·2° C.), and the absolute maximum and minimum, 99·7° and 50·2° F.

(37·7° and 10·1° C.).

The average rainfall for nine years was as follows:--

====+====+====+====+====+===+====+====+====+=====+====+====+====+=====

|Jan.|Feb.|Mar.|Apl.|May|June|July|Aug.|Sept.|Oct.|Nov.|Dec.|Year

----+----+----+----+----+---+----+----+----+-----+----+----+----+-----

Ins.|2·5 |3·3 |3·7 |4·8 |4·2|3·4 |2·5 |3·3 | 4·8 |4·8 |5·3 |3·2 | 40·6

Mm. | 63 | 84 | 94 |122 |106| 87 | 63 | 83 | 122 |122 |136 | 80 |1,160

====+====+====+====+====+===+====+====+====+=====+====+====+====+=====

In the north (Uganda) the climate is warm and moist, though without

excessive rainfall, but the air is a good deal drier along the southern

coast.

In Tanganyika, in lat. 4° S., long. 29° E. (E.F., 2,670, E.M., 813), the

mean annual temperature is 76·7° F. (24·8° C.), the mean of the hottest

month (of October) being 81·7° F. (27·6° C.), and of the coolest, in

December, 74·2° F. (23·4° C.), the extremes being 90·7° and 64·4° F.

(32·6° and 18° C.). The rains occur in April and May and November and

December, while from June to September is dry, the annual rainfall being

50 ins. (1,270 mm.).

Further south, Zoruba, in Nyassaland, has a total rainfall of 62·23 ins.

(1,581 mm.), falling on 144 days in the year, but should otherwise be a

pleasant climate, as the relative humidity is usually low.

ZORUBA. LAT. 16° S. E.F., 1800. E.M., 548.

========+====+======+===========+===========+=====+=============+=====

| |Temperature|Temperature| Hu- | | of

+----+------+----+------+----+------+midi-+-----+-------+Rainy

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | ty | Ins.| ~Mm.~ | Days

| | | | | | | at 2| | |

| | | | | | | p.m.| | |

--------+----+------+----+------+----+------+-----+-----+-------+-----

January |69·8|~21~ |81·2|~27·3~|65·9|~18·9~| 78 |11·62|~295~ | 27

February|66·7|~19·3~|77·6|~25·3~|63·7|~17·6~| 74 |15·42|~391~ | 20

March |66·7|~19·3~|78·9|~26·1~|64·7|~18·2~| 90 | 7·60|~193~ | 23

April |64·4|~18·1~|75·4|~24·2~|61·7|~16·5~| 76 |11·74|~298·5~| 14

May |61·1|~16·1~|76·9|~25·0~|58·0|~14·4~| 65 | 0·37| ~9·0~| 7

June |57·1|~13·9~|68·4|~20·3~|54·4|~12·5~| 66 | 2·55| ~64·8~| 12

July |55·0|~12·8~|68·8|~20·5~|52·9|~11·7~| 65 | 0·87| ~21·8~| 6

August |55·4|~13·1~|71·4|~21·9~|52·3|~11·3~| 51 | 0·15| ~3·8~| 4

ber |62·7|~17·0~|79·0|~26·1~|58·1|~14·4~| 48 | 1·80| ~45·7~| 4

October |68·5|~20·3~|85·4|~29·7~|62·6|~16·9~| 53 | ·95| ~24·1~| 4

November|72·0|~22·2~|88·3|~31·3~|67·1|~19·4~| 53 | ·35| ~8·9~| 4

December|73·2|~23·0~|83·6|~28·6~|65·6|~18·6~| 66 | 8·81|~223·8~| 19

========+====+======+====+======+====+======+=====+=====+=======+=====

The capital, Blantyre, at E.F., 3,280, E.M., 1,000, is naturally even

cooler, but has a heavier rainfall, distributed as below:--

====+=====+=====+=====+=====+=====+====+

| Jan.| Feb.| Mar.| Apl.| May |June|

----+-----+-----+-----+-----+-----+----+

Ins.|19·51|17·60|14·48|13·77| 4·05|3·28|

Mm. |484·6| 447 | 368 |349·5|102·9|83·7|

====+=====+=====+=====+=====+=====+====+

====+====+====+=====+=====+=====+=====

|July|Aug.|Sept.| Oct.| Nov.| Dec.

----+----+----+-----+-----+-----+-----

Ins.|3·34|1·56| 1·83| 4·13| 5·54|15·35

Mm. |85·1|39·5| 46·8|105·3| 140| 390

====+====+====+=====+=====+=====+=====

_The Congo Basin._--The climate of the basin of the Congo is notoriously

unhealthy, especially as the portion as yet opened up seldom extends far

beyond the low malarious banks of the great river and its tributaries.

The warmest month is February or March, and the coldest July or August.

Hann gives the following table of the temperatures of the following

stations:--

===============+========+===========+============+============

Station |Latitude|Mean Annual|Mean Temper-|Mean Temper-

| |Temperature| ature of | ature of

| | | Warmest | Coldest

| | | Month | Month

| |----+------+-----+------+-----+------

| | F. | ~C.~ | F. | ~C.~ | F. | ~C.~

---------------+--------+----+------+-----+------+-----+------

Luluaberg |5·9° S. |81·3|~27·4~| 81·7|~27·6~| 80·8|~27·1~

Congo, mouth of|6·0° S. |76·8|~24·9~| 80·5|~26·9~| 70·9|~21·6~

Vivi |5·7° S. |77·2|~25·1~| 80·5|~26·9~| 71·7|~22·0~

San Salvador |6·3° S. |77·9|~25·5~| 81·0|~27·2~| 72·8|~22·7~

Brazzaville |4·3° S. |81·2|~27·3~| 84·7|~29·3~| 75·2|~24·0~

Bolobo |2·2° S. |80·5|~26·9~| 81·5|~27·5~| 79·4|~26·3~

Equatorville |0·0 |79·1|~26·2~| 80·6|~27·0~| 78·2|~25·7~

Bangala |1·5° N. |78·9|~26·0~| 80·8|~27·1~| 77·7|~25·4~

===============+========+====+======+=====+======+=====+======

These are typical equatorial climates, the greatest range between the

means of the coldest and hottest months being at most 9·5° F. (5·3° C.),

while in one case the range is less than one degree of the Fahrenheit

scale, and though the temperatures are in no case excessive, the

dampness of the atmosphere makes the heat of a very trying character,

especially in certain localities, as at Stanley’s Pool, where during

August and September there are certain peculiar night-winds which, not

unfrequently, are the cause of cases of heat apoplexy, and this although

the highest temperature recorded is but 97°, at Brazzaville.

There are two rainy seasons, in April and November. The dry period falls

in June and July, but is not very marked in the interior.

The table on next page will give an idea of the amount and distribution

of the rainfall.

_On the West Coast_, at Bathurst, the highest temperature occurs in

October, during the period of the greater rains, the annual extremes

being 98·8° F. (37·1° C.) and 57·4° F. (14·1° C.); the greatest daily

variation of temperature being met with during the dry season, January

to April, when it amounts to about 20° F. (11·5° C.). The rainfall

varied during eleven years from about 32 ins. (813 mm.) to 78 ins.

(1,980 mm.). In December, a cool morning breeze known as the Harmattan

sets in, and continues till February or March. The rains begin in June

and end in September.

MONTHLY RAINFALL IN THE CONGO BASIN.

=========+=======================================

Month | STATION.

+-----------+-------------+-------------

| Congo, | Lower Congo | Bolobo

| Mouth of | |

+-----+-----+-----+-------+-----+-------

| Ins.|~Mm.~| Ins.| ~Mm.~ | Ins.| ~Mm.~

---------+-----+-----+-----+-------+-----+-------

January | 3·70| ~94~| 2·93| ~74~| 5·0 | ~127~

February | 3·12| ~79~| 3·87| ~98~| 6·97| ~177~

March | 4·09|~104~| 4·73| ~120~| 4·61| ~117~

April | 3·86| ~98~| 8·87| ~225~| 7·17| ~182~

May | 2·98| ~76~| 2·84| ~72~| 5·64| ~143~

June | 0·23| ~6~| 0·19| ~5~| 0·39| ~10~

July | 0 | ~0~| 0 | ~0~| 0·04| ~1~

August | 0·08| ~2~| 0 | ~0~| 2·60| ~66~

September| 0·16| ~4~| 0 | ~0~| 3·98| ~101~

October | 0·48| ~12~| 2·17| ~55~| 6·54| ~166~

November | 3·95|~100~| 8·31| ~211~| 9·58| ~243~

December | 2·28| ~58~| 4·64| ~118~|10·80| ~260~

---------+-----+-----+-----+-------+-----+-------

Year |24·95|~633~|39·85|~1,008~|62·7 |~1,593~

=========+=====+=====+=====+=======+=====+=======

_At Sierra Leone_, in spite of its lying north of the equator, the

distribution of the monthly temperature resembles that of the Southern

Hemisphere, the minimum falling in August, while the hot season lasts

from February to May. The mean annual temperature is 77·6° F. (25·4°

C.), and the average annual extreme temperatures 97·5° F. (36·4° C.) and

64·8° F. (18·2° C.). No month is absolutely rainless, and the annual

rainfall is very heavy, ranging from 100 ins. (2,540 mm.) to 204·5 ins.

(5,230 mm.).

Curiously enough, the Cape Verd Islands are very dry, although they

agree generally as to temperature with the coast, tempered by their

insular position and the influence of the trade wind, having a rainfall

of only about 10 ins. (260 mm.), the most rainy month being September.

_Gulf of Guinea._--Along this coast there is a double rainy season; the

greater from March to the end of July, and the lesser in October and

November; with the dry season in August and September, and the cool

Harmattan blowing between November and March. In speaking of the

Harmattan as a cool breeze, it must be remembered that one refers only

to the sensations produced by it; for as a matter of fact, it has no

appreciable effect on the mean temperature, and feels cool only by

virtue of the accelerated evaporation from the skin caused by its

intense dryness. On the coast it really raises the mid-day temperatures,

although it renders the mornings and evenings cooler. In the interior

the Harmattan may figure indeed as a hot wind, and may be additionally

disagreeable on account of the red dust it carries.

The rainfall is everywhere very heavy, that of the Cameroon district

reaching the enormous figure of 350 ins. (8,970 mm.), the second

greatest in the world.

The mean annual temperature is about 77° F. (25° C.), with annual

extremes of 89·6° F. (32° C.) and 68° F. (20° C).

The following table of the climatic data for the coast of British

Nigeria will give a fair idea of the conditions that will be met with in

the coast towns of the group of colonies in this region:--

OLD CALABAR. LAT. 4° 58′ N.; LONG. 8° 17′ E.

=========+===========+===========+===========+======+

| | | | ity |

+----+------+----+------+----+------+ Per +

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | Cent.|

---------+----+------+----+------+----+------+------+

January |83·4|~28·6~| 90 |~32·2~| 68 |~20·0~| 78·8 |

February |86·5|~30·3~| 94 |~34·4~| 72 |~22·2~| 78·1 |

March |84·8|~29·2~| 94 |~34·4~| 71 |~21·7~| 81·6 |

April |85·5|~29·7~| 93 |~33·9~| 71 |~21·7~| 75·8 |

May |81·9|~27·8~| 94 |~34·4~| 75 |~23·9~| 77·6 |

June |80·8|~27·0~| 92 |~33·3~| 71 |~21·7~| 84·4 |

July |77·9|~25·5~| 90 |~32·2~| 70 |~21·1~| 85·8 |

August |77·1|~25·0~| 86 |~30·0~| 70 |~21·1~| 88·2 |

September|80·8|~27·0~| 92 |~33·3~| 70 |~21·1~| 85·7 |

October |82·3|~28·0~| 91 |~32·8~| 70 |~21·1~| 83·6 |

November |82·3|~28·0~| 91 |~32·8~| 71 |~21·7~| 83·9 |

December |81·9|~27·8~| 89 |~31·7~| 70 |~21·1~| 83·6 |

---------+----+------+----+------+----+------+------+

Year |82·2|~28·0~| 94 |~34·4~| 68 |~20·0~| 82·1 |

=========+====+======+====+======+====+======+======+

=========+==============+=====

Month | Rainfall | Num-

| | ber

| | of

| |Rainy

+------+-------+Days

| Ins. | ~Mm.~ |

---------+------+-------+-----

January | 2·68| ~68·1~| 1

February | 6·69|~170·0~| 5

March | 7·70|~195·6~| 8

April | 11·01|~279·5~| 10

May | 10·95|~279·0~| 19

June | 32·59|~827·0~| 22

July | 13·61|~345·4~| 25

August | 6·39|~162·4~| 15

September| 11·84|~300·0~| 25

October | 9·38|~238·0~| 17

November | 11·34|~288·3~| 12

December | 1·32| ~33·6~| 1

---------+------+-------+-----

Year |119·50|~303·6~| 150

=========+======+=======+=====

The remarkable uniformity of the temperature data is very striking. In

the interior of Nigeria, however, much higher temperatures are

experienced, especially at the times when the hot Harmattan is blowing

off the northern deserts, the noon temperature at such times being

rarely under 100° F. (37·8° C).

As we get farther south the temperature moderates and the rainfall

rapidly diminishes; the mean temperature in Angola being no more than

68° F. (20° C.), while in the elevated interior the climate is neither

disagreeable nor unhealthy.

Dr. Yale Massey sends me the following information from his Mission

station in the Benguela district, at 4,700 feet, lat. _circa_ 12° S.;

and long. 17° E. “The distinctly wet months are from October to April

inclusive, and this is also the hot season. There are usually a few

showers in September, and rarely some in May, and during the dry season

there is usually a strong breeze. In the wet season the mid-day

temperature ranges from 80° to 100° F., at night from 45° to 60° F.;

while during the dry weather the mid-day temperature is from 70° to 90°

F., and at night even slight frost may occur. As might be expected from

the elevation and climate, this is a generally healthy locality, but

there is a certain amount of fever, most of the cases occurring in April

and May.”

_East Coast._--The reputation borne by the east coast is scarcely more

enviable than that of the western, the accounts of travellers voyaging

on the Zambesi being generally alternate wails on attacks of mosquitoes

and upsets from hippopotami. The rainfall is, however, much lighter, and

at corresponding latitudes the temperatures generally seem somewhat

lower.

Owing to the presence of a considerable Arab element, the population

have attained, in some places, a larger grade of civilisation than is

the case on the west coast, so that the introduction of hygienic

measures might be somewhat more practicable, albeit that Arab

civilisation, _per se_, has hardly reached the stage of promoting

sanitation.

The two following tables of a tropical and subtropical station, each on

this coast, will give some general conception of the conditions

prevailing.

ZANZIBAR ISLAND. LAT. _circa_ 7° 30′ S.

=========+=============+=============+================

Month | Mean Maximum| Mean Minimum| Rainfall

| Temperature | Temperature |

---------+------+------+------+------+-----+----------

| F. | ~C.~ | F. | ~C.~ |Ins. | ~Mm.~

---------+------+------+------+------+-----+----------

January | 86·1 |~30·0~| 79·6 |~26·5~| 3·26| ~82·6~

February | 87·0 |~30·6~| 80·3 |~26·8~| 1·51| ~38·3~

March | 86·3 |~30·2~| 79·3 |~26·3~| 6·24| ~159·1~

April | 84·7 |~29·3~| 77·6 |~25·4~|11·94| ~303·3~

May | 82·4 |~28·0~| 75·6 |~24·3~|10·23| ~250·2~

June | 81·5 |~27·5~| 74·2 |~23·5~| 1·36| ~34·7~

July | 80·2 |~26·8~| 72·7 |~22·6~| 2·75| ~69·8~

August | 81·8 |~27·0~| 72·7 |~22·6~| 1·68| ~43·0~

September| 82·0 |~27·8~| 73·4 |~23·0~| 2·10| ~53·3~

October | 83·2 |~28·1~| 75·3 |~24·0~| 3·74| ~95·1~

November | 83·7 |~28·7~| 77·1 |~25·1~| 8·23| ~209·1~

December | 85·8 |~29·8~| 79·5 |~26·4~| 4·18| ~106·3~

---------+------+------+------+------+-----+----------

Year | 83·6 |~28·7~| 76·4 |~24·6~|57·25|~1,454·2~

=========+======+======+======+======+=====+==========

NATAL, DURBAN. LAT. 29° 50′ S.; NEAR SEA-LEVEL. (1902.)

=========+===========+============+===========+===============+=======

+----+------+-----+------+----+------+-----+---------+ Rainy

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ |Ins. | ~Mm.~ | Days

---------+----+------+-----+------+----+------+-----+---------+-------

January |74·0|~23·3~| 92·1|~33·4~|56·4|~13·6~| 6·53| ~166·2~| 23

February |78·2|~25·7~| 95·2|~35·1~|60·5|~15·8~| 2·09| ~53·2~| 12

March |74·5|~23·6~| 93·8|~34·3~|59·2|~15·1~|10·23| ~256·5~| 20

April |70·1|~21·1~| 86·2|~30·1~|56·9|~13·8~| 2·52| ~64·0~| 9

May |66·5|~19·2~| 83·5|~28·6~|52·0|~11·1~| 1·21| ~30·6~| 10

June |61·6|~16·5~| 78·3|~25·7~|47·4| ~8·6~| 0·73| ~18·0~| 3

July |62·0|~16·7~| 88·0|~31·1~|49·5| ~9·7~| 0·27| ~7·0~| 4

August |63·5|~17·5~| 79·0|~26·1~|48·4| ~9·2~| 3·90| ~99·1~| 12

September|67·1|~19·5~|105·6|~40·9~|51·5|~10·8~| 2·54| ~64·7~| 13

October |69·6|~20·8~| 91·2|~32·9~|51·3|~10·7~| 2·23| ~56·6~| 17

November |70·9|~21·6~| 92·3|~33·5~|57·1|~13·9~| 5·15| ~130·8~| 19

December |75·2|~24·0~| 91·4|~33·1~|58·2|~14·5~| 3·96| ~100·4~| 18

---------+----+------+-----+------+----+------+-----+---------+-------

Year |69·4|~20·8~|105·6|~40·9~|47·4| ~8·6~|41·18|~1,047·0~| 160

=========+====+======+=====+======+====+======+=====+=========+=======

_Madagascar._--With the exception of the littoral, which is rather warm

and extremely malarious, the greater part of this island is too elevated

to present a really hot climate, but the rainfall in the interior is

rather heavier than on the mainland, that of the capital, Antananarivo,

being 52·4 ins. (1,331 mm.), which is distributed as follows:--

MONTHLY RAINFALL OF ANTANANARIVO. E.F., 4,850; E.M., 1,478.

====+=====+====+=====+=====+====+====+====+====+=====+====+====+====

| Jan.|Feb.|March|April| May|June|July|Aug.|Sept.|Oct.|Nov.|Dec.

----+-----+----+-----+-----+----+----+----+----+-----+----+----+----

Ins.|11·54|9·28|7·36 | 2·00|0·71|0·33|0·20|0·28| 3·18|3·51|5·25|11·0

Mm. | 294 | 236| 187 | 51 | 18 | 8 | 5 | 7 | 17 | 89 | 133| 280

====+=====+====+=====+=====+====+====+====+====+=====+====+====+====

_The Island of Mauritius._--Latitude _circa_ 20° 20′ S. The mean annual

temperature of Port Louis is 77·2° F. (25·1° C.), the absolute extremes

of temperature in nineteen years being 89° and 53·5° F. (31·6° and 11·9°

C.), and the mean relative humidity 74 per cent., so that in the matter

of heat there is nothing to be feared; but unfortunately malaria, which

was quite unknown in the earlier days of its colonisation, is now very

rife and of a very obstinate type. The rainfall amounts to 74·5 ins.

(1,892 mm.), which is rather heavier than that of Madagascar, and is

distributed as below:--

MONTHLY RAINFALL OF PORT LOUIS, MAURITIUS; NEAR SEA-LEVEL.

====+=====+====+=====+=====+====+====+====+====+=====+====+====+====

|Jan. |Feb.|March|April|May |June|July|Aug.|Sept.|Oct.|Nov.|Dec.

----+-----+----+-----+-----+----+----+----+----+-----+----+----+----

Ins.|11·55|8·18|11·35|9·14 |5·73|4·65|4·25|3·86|2·71 |2·64|3·24|6·98

Mm. | 293 |208 | 288|232 |145 |118 |108 | 98 | 69 | 67 | 82 |177

====+=====+====+=====+=====+====+====+====+====+=====+====+====+====

The southernmost portions of Africa, Cape Colony, &c., do not belong to

the category of hot climates, either in climate or in their diseases,

and so need not be considered here.

_Red Sea and its Coasts, including Somaliland._--The horrors of the

climate of the Red Sea are too well known to need comment. The whole

region is almost rainless, subject to suffocating calms, and the

presence of the large, but completely land-locked, sheet of water

renders the relative humidity constantly high. Moreover, the whole basin

is comparatively shallow, so that it becomes highly warmed even in its

depths. At its southern end the temperature of the water at the surface

may reach 95° F. (35° C.), and 90° F. (32·2° C.) has been registered at

a depth of 5 fathoms. In the Gulf of Suez, pleasantly fresh days may be

met with during winter, but in the south the mean temperature of a day

seldom falls below 80° F. (26·7° C.), and in July the mean maximum

temperature exceeds 108° F. (42° C.) July is the hottest month, but

there is little to choose between the discomforts of any of the four

months, June to September. The least hot month is January, but the

climate is a singularly uniform one, the night bringing comparatively

little relief, and when followed by a breeze of about the same speed as

the ship, cases have occurred in which steamers have actually been

obliged to put about and steam against the wind, in order to prevent the

crew from falling victims to heat apoplexy.

North of lat. 19°, the prevailing winds are from the north or

north-west, while in the south the predominating winds are from the

south and south-east, between the two lying a belt of variable winds.

From June to August north-west winds prevail over the whole Red Sea.

This is known as the “Kamsin,” or fifty days’ wind, the word being

derived from the Arabic root of that numeral, which, originally,

intensely hot and dry, rapidly takes up moisture from the water, and is

hence particularly insupportable on the Arabian side of the sea; though

the fine sand with which it is loaded makes it equally objectionable

from another point of view on the African side. Its velocity is often

considerable, and under such circumstances may be even dangerous to the

lives of those who are so unfortunate as to be exposed to its fury in

the open desert. The extremely fine dust penetrates everywhere in spite

of closed doors and windows, reaching even ships far out at sea.

Fortunately, on the coast it is generally a good deal modified by

sea-breezes springing up in the afternoon, but there is also a tendency

to fall dead calm at night, under which circumstances the dark hours are

even more intolerable than those of the day.

The following table of the principal climatic data of Massawa in the

Italian colony of Erythrea, compiled from data contained in a pamphlet

by Dr. Giovani Petella, of the Royal Italian Navy, gives a good idea of

the character of the climate of the Red Sea littoral.

MASSAWA. LAT. 16° N.; NEAR SEA-LEVEL.

=========+===========+============+===========+=====+===========+=====

| | Temperature|Temperature| Hu- | | of

+----+------+-----+------+----+------+midi-+----+------+Rainy

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | ty |Ins.| ~Mm.~| Days

| | | | | | | % | | |

---------+----+------+-----+------+----+------+-----+----+------+-----

January |78·0|~25·6~| 90·4|~32·4~|68·0|~20·0~| 75 |2·05|~52·1~| 5·2

February |78·9|~26·0~| 92·2|~33·4~|68·4|~20·2~| 76 |0·63|~16·2~| 1·6

March |81·0|~27·2~| 94·8|~34·9~|70·1|~21·2~| 74 |0·68|~17·5~| 1·7

April |84·3|~29·0~| 98·2|~36·8~|72·8|~22·6~| 69 |0·11| ~2·5~| ·2

May |88·5|~31·3~|101·7|~38·7~|76·6|~24·7~| 66 |0·56|~14·1~| 1·4

June |92·4|~33·5~|105·9|~41·0~|80·7|~27·0~| 51 | -- | -- | --

July |94·7|~34·8~|108·5|~42·5~|84·5|~29·2~| 56 |0·13| ~3·3~| 1·3

August |94·6|~34·7~|106·7|~41·5~|83·4|~28·5~| 57 |0·26| ~5·7~| 1·7

September|92·0|~33·3~|103·0|~39·4~|78·2|~25·7~| 60 |0·17| ~4·0~| 1·0

October |89·0|~31·7~| 98·7|~37·0~|77·2|~25·1~| 60 |0·35| ~9·0~| 1·0

November |84·3|~29·0~| 95·2|~35·1~|75·0|~23·8~| 65 |0·78|~20·0~| 2·1

December |80·7|~27·0~| 92·0|~33·3~|69·5|~20·8~| 70 |2·27|~57·6~| 3·7

=========+====+======+=====+======+====+======+=====+====+======+=====

The total rainfall amounts only to 7·86 ins. (198 mm.), falling on 29·2

days in the year, but the amount and distribution is very capricious,

varying greatly in different years. In so far, however, as Massawa can

be said to possess a rainy season at all, the wet weather comes in the

winter, instead of about August, as is normally the case in the Tropics

of the Northern Hemisphere.

Sometimes a whole year may be practically rainless, as for example 1885,

in which only 41·2 mm. (about 1¹⁄₂ ins.) was collected, whereas 1891 had

the respectable rainfall of 500 mm. (or 19¹⁄₂ ins.). Apparently,

however, it never rains in June.

Owing to the antiseptic powers of the intense light and heat, the place

is singularly free from zymotic diseases, the cases of fever being

usually not malarial, but truly climatic.

For the greater part of the year the skin is kept in a continuous bath

of perspiration, and accordingly prickly heat in its most acute form,

with the usual sequel of boils, is very common; as also, of course, are

heatstroke and less acute forms of nervous prostration. During the

continuance of the Kamsin Dr. Petella finds that the temperature of even

strong and healthy individuals is raised distinctly above the normal.

The extreme character of the climate of Suakim, the frequent scene of

British military activity, may be gathered from the following nearly

complete table for portions of the years 1902-1903.

SUAKIM. LAT. 19° 5′ N. NEAR SEA-LEVEL.

=====+============+===========+============+===+=====+================

| Temperature|Temperature| | o | Hu- |

+-----+------+----+------+----+-------+ u |midi-|

| F. | ~C.~ | F. | ~C.~ |Ins.| ~Mm.~ | d | ty |

| | | | | | | s | |

-----+-----+------+----+------+----+-------+---+-----+----------------

Jan. | 78·5|~25·8~|68·4|~20·2~|1·17| ~29·7~|4·5| 71 |N.N.W., occasio-

Feb. | 79·0|~26·7~|70·4|~21·3~|0·68| ~17·0~|4·8| 78 |N.W., shifting

Mar. | 82·5|~28·1~|71·9|~22·1~|0 | ~0~ |2·1| 90 |Ditto, ditto

May | 95·0|~35·0~|76·1|~24·5~|0 | ~0~ |0·5| 78 |Ditto, ditto

June |100·2|~37·9~|78·0|~25·6~|0·13| ~3·0~|1·2| 69 |Variable, but

July |107·8|~42·1~|82·0|~27·8~|0·36| ~9·3~|1·5| 48 |S.W. to S.,

Aug. |112·0|~44·4~|84·4|~29·1~|0 | ~0~ |1·3| 68 |Ditto, ditto

Oct. | 92·0|~33·3~|78·0|~25·6~|4·80|~122·0~|3·5| 75 |N.W. to W.,

Nov. | 86·5|~30·3~|75·9|~24·3~|6·10|~154·9~|5·6| 78 |Ditto, ditto

Dec. | 81·0|~27·2~|69·5|~20·8~|2·02| ~51·5~|4·5| 78 |Ditto, ditto

=====+=====+======+====+======+====+=======+===+=====+================

No European constitution could, however, endure such climates for any

considerable time with impunity without periods of relief in a more

moderate climate, and it is therefore fortunate that, owing to

configuration of the Colony of Erythrea, the inland portion of which for

the most part consists of elevated plateaux and mountains; these extreme

conditions of heat and moisture are limited to a comparatively narrow

belt of country, consisting of plains formed of slightly elevated coral

formation, and the foothills which gradually rise to elevations at which

the climate is necessarily temperate, some of the peaks reaching over

7,000 feet above the sea.

The progressive improvement of climate as one gains increasing

elevations, even where that at the sea-level is of the most extreme

character, is instructively shown in the table on next page, taken from

Dr. Petella’s pamphlet.

TABLE SHOWING THE MEAN MONTHLY TEMPERATURE OF FOUR STATIONS IN ERYTHREA

AT VARIOUS ELEVATIONS, THE DIMINUTION OF TEMPERATURE BEING EQUIVALENT TO

ABOUT 1° F. FOR EVERY 300 FEET OF ELEVATION, OR 1° C. TO EACH 150

METRES.

============+===========+===========+===========+============

Month | Massawa, | Ghenda, | Cheren, | Asmara,

| 6 m. | 962 m. | 1,460 m. | 2,327 m.

| elevation | elevation | elevation | elevation

| = 18 ft. |= 3,165 ft.|= 4,790 ft.|= 7,533 ft.

+----+------+----+------+----+------+----+-------

| F. | ~C.~ | F. | ~C.~ | F. | ~C.~ | F. | ~C.~

------------+----+------+----+------+----+------+----+-------

January |78·0|~25·6~|65·2|~18·4~|63·3|~17·3~|68·8|~14·9~

February |78·9|~26·0~|69·4|~20·8~|67·0|~19·4~|61·4|~16·3~

March |79·4|~26·3~|73·3|~22·9~|72·0|~22·2~|61·5|~16·4~

April |84·3|~29·0~|78·6|~25·8~|77·0|~24·9~|62·8|~17·1~

May |88·5|~31·3~|79·6|~26·3~|75·8|~24·3~|63·5|~17·5~

June |92·4|~33·3~|84·1|~28·9~|76·5|~24·7~|63·5|~17·5~

July |94·7|~34·8~|87·2|~30·7~|72·7|~22·6~|61·5|~16·4~

August |94·5|~34·7~|83·4|~28·5~|68·0|~20·0~|61·4|~16·3~

September |92·9|~33·8~|84·5|~29·2~|68·4|~20·2~|62·5|~16·9~

October |89·2|~31·8~|76·8|~24·9~|67·4|~19·6~|56·5|~13·6~

November |84·3|~29·0~|72·3|~22·4~|65·2|~18·4~|58·4|~14·6~

December |80·7|~27·0~|65·8|~18·7~|63·3|~17·3~|58·8|~14·9~

------------+----+------+----+------+----+------+----+-------

Annual Means|86·5|~30·3~|76·7|~24·8~|69·7|~20·9~|60·0|~16·5~

============+====+======+====+======+====+======+====+=======

In these elevated regions, a little away from the coast, there is a

definite, though not very abundant, rainy season, and the direction of

the prevailing winds is normal for these latitudes, _i.e._, north-east

during the winter and south-west during the monsoon, which, however,

breaks a good deal later here than at corresponding latitudes on the

eastern side of the Arabian sea. More complete data of Addi Ugri, an

Italian sanatorium on one of these Erythrean hill-stations, are

extracted below from a pamphlet by Captain Tancredi, an Engineer

officer.

The hottest time of the year is, it will be noticed, in the spring, and

the rainy season takes place at the normal time in July and August,

after the setting in of the south-west monsoon. There is also a

secondary period of rainfall about February and March, corresponding to

our “chota bursat” in India.

From the inspection of the table on next page it will be seen that the

climate must be an exceptionally pleasant one, the mean temperature of

the year corresponding to that of Southern Italy, though the range of

temperature is less than a third of that of Palermo and other

Mediterranean ports. The climate is also said to be very healthy,

though there is generally a certain amount of malaria to be met with

about the drying up of the rains. Its uniformity and mildness, coupled

as it is with great dryness, suggests that the site might well be

utilised for certain forms of chest disease.

CLIMATE OF ADDI-UGRI, ERYTHREA (SERAHÈ). LAT. 14° 53′ N.; LONG. 38° 48′

40″ E. ELEVATION 6,633 FEET.

========+===========+===========+===========+=====+=============+=====

| |Temperature|Temperature| Hu- | | of

+----+------+----+------+----+------+midi-+-----+-------+Rainy

| F. | ~C.~ | F.| ~C.~ | F. | ~C.~ | ty | Ins.| ~Mm. ~| Days

| | | | | | | % | | |

--------+----+------+----+------+----+------+-----+-----+-------+-----

January |64·9|~18·2~|79·0|~26·0~|51·6|~10·9~| 39·6| 0·02| ~0·3~| 2

February|66·3|~19·0~|81·2|~27·4~|51·9|~11·0~| 28·6| 0·11| ~2·7~| 1·6

March |70·6|~21·4~|87·0|~30·6~|55·5|~13·1~| 30·0| 0·62| ~15·4~| 6·6

April |70·4|~21·3~|85·5|~29·7~|56·5|~13·6~| 35·3| 0·91| ~22·8~| 9·3

May |70·6|~21·4~|84·5|~29·1~|58·2|~14·5~| 36·6| 1·85| ~46·2~| 10·3

June |69·5|~20·8~|82·3|~27·9~|60·4|~15·7~| 39·1| 2·41| ~60·6~| 15·3

July |64·3|~17·9~|73·6|~23·2~|54·6|~12·6~| 71·9| 5·30|~134·9~| 25·0

August |63·8|~17·6~|73·4|~22·9~|54·6|~12·5~| 74·1| 7·05|~179·1~| 24·3

ber |67·5|~19·7~|78·6|~25·9~|56·2|~13·3~| 53·4| 1·45| ~36·8~| 6·6

October |67·6|~19·7~|80·3|~26·8~|54·4|~12·4~| 53·0| 0·65| ~16·5~| 3

November|65·4|~18·5~|78·6|~25·8~|52·5|~11·3~| 43·6| 0·19| ~4·2~| 1·6

December|63·5|~17·4~|78·0|~25·5~|50·0| ~9·9~| 42·3| 0·32| ~8·3~| 1·6

--------+----+------+----+------+----+------+-----+-----+-------+-----

Year |66·9|~19·4~|80·2|~26·8~|54·7|~12·6~| 45·6|20·2 |~513·0~|107·2

========+====+======+====+======+====+======+=====+=====+=======+=====

Travelling, however, in Somaliland is necessarily arduous, as the

country is nearly impassable during the short rainy season, and intense

heat and great suffering have to be encountered in the low-lying

valleys, owing to the waterless character of the country and the

intensely desiccating effects of the air, which, elsewhere than on the

coast, is intensely dry. The frequent dust storms are also a source of

much discomfort and even of danger.

Climate and Health in Hot Countries and the Outlines of Tropical Climatology A Popular Treatise on Personal Hygiene in the Hotter Parts of the World, and on the Climates That Will Be Met Within Them. · 第 9 / 11 章

A very broad belt of the earth’s surface is occupied by countries that