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.

The climate of California is undoubtedly one of the finest in the world. Like the rest of the western seaboard of America, the rainfall is small, but there is always sufficient water for cultivation by the agency of irrigation; and the clearness of the atmosphere and genial temperature renders this State the ideal of the physician in search for health resorts. Apart, indeed, from the excitements of “euchre” and the germs introduced by the Chinese settler, it seems difficult to understand why anyone should suffer illness in such a climate as that of Los Angeles, whose principal characteristics are epitomised in the above table. Let us hope, however, that “Ah Sin” has not driven the angels too far away for recall by the rapidly advancing sanitation of American civilisation.

With a total rainfall of only 15·43 ins. (392 mm.), and a remarkably high percentage of hours of sunshine, even during the rainy months, one begins to understand how it is that a Californian fellow-member of the Golf Club of Rome used to complain of the “gloom” of a Roman winter. The one drawback is the enormous daily range of over 50° F., which must be necessarily trying to delicate subjects who neglect obvious precautions; but avoidance of the fierce heat out of doors of the afternoon, and the chill that follows sunset, should suffice to neutralise this defect. Across the sierras, in Texas the rainfall remains very scanty, amounting to no more than 9·8 ins. (250 mm.) in the district of El Paso, but improves steadily as we approach the eastern frontier, where it reaches 52 ins. (1,320 mm.) at Galveston, on the coast of the Gulf of Mexico. This place is regarded as a health resort for the Southern States; Dr. Solly, the American authority on medical climatology, writes:—

“The climate of Galveston, in the Gulf of Mexico, is warm, mild and humid. Occasionally, there are winters when the temperature does not fall below 32°. During the past twenty years there have been thirteen years in which the temperature has not fallen below 24°, and but two years below 20°. The seasonal mean temperatures are: Winter, 55°; Spring, 69°; Summer, 83°; Autumn, 71°. The annual mean is 70°. Monthly mean for January, 53°; for July, 84°. The extreme temperature record is 98°, and the minimum 20°. The mean rainfall is 51 inches, distributed as follows: Winter, 11·5 inches; Spring, 10·2 inches; Summer, 13·3 inches; Autumn, 16·6 inches. The heaviest rain takes place in September, and the least in February and July. The mean annual relative humidity is 77 per cent.; for Winter, 81 per cent. Wind movement averages 11·1 miles, the prevailing winds being from S. and S.E. The highest winds occur in winter and blow from the N., but the average ‘northers’ of upper Texas are but little felt in the Gulf of Mexico.”

Proceeding westward along the Mexican Gulf we find the climate grows steadily moister, New Orleans, which is placed very nearly in the middle of its northern coast, presenting the following climatic factors.

The amenity of the climate of Florida is proverbial, as the maxima rarely run so high, and the annual and daily range is much smaller than is the case further west, owing to the effect of the Gulf Stream, which sweeps out past its projecting shore. On this account there is an almost entire absence of frost, and the State has become celebrated for its cultivation of oranges, a fruit which is at once nipped by any approach to freezing point. Dr. Solly describes it as follows:—

“The climate is marine in character, and is very equable and temperate for its latitude. The mean annual temperature runs from 69° at Sanford to 79·8° at Jacksonville; for the winter, the variation is from 54·6° at Pensacola to 66·5°, at Jupiter. Frost, snow and ice are very rare. Annual rainfall varies from 53·19 inches at Pensacola to 57·16 at Cedar Keys; of this, one half usually occurs in the summer. The mean relative humidity varies from 76 per cent. at Pensacola to 80 at Cedar Keys. In the winter months it is from 76 to 87 per cent. The total number of rainy days ranged from 103·8 at Cedar Keys to 124·1 at Pensacola, and the number of cloudy days in the same places was 66.8 and 84·5. Dr. Hall, while admitting the prevalence of malaria, states that there are many places quite free from it, and that it is generally diminishing.”

Mexico.

—Extending, as it does, completely across the southern portion of the North American Continent, the climate of Mexico presents the same sequence from the drought of the eastern to the moderately ample rainfall of the western coasts; and here too, there are places in the central highlands that are much drier than any to be found on either coast. These points are illustrated in the table on following page.

The corresponding data as to temperature are given below.

Central America and the Isthmus of Panama.

—This portion of the American continent is notoriously unhealthy, especially along the only routes practicable for an inter-oceanic canal.

It is said that the construction of the railway across Panama cost a human life for every sleeper that was laid.

Much of this is due to malaria, but yellow fever also frequently attacked the workers, and it is to be hoped that as both these diseases are known to be capable of transmission only by the agency of mosquitoes, that a rational prophylaxis against the bites of these insects will form part of the sanitary programme of the huge work that is now being proceeded with. In any case, when the new canal comes to be finished it will behove passengers by the mail boats to provide themselves with mosquito nets for this portion of the voyage.

The north-east Trades dominate the Atlantic coast of these regions throughout the year, but on the Pacific side, during the summer months, a southerly breeze takes its place.

The rainfall is very heavy, but even here, in spite of the narrowness of the dividing belt of land, the comparative dryness of the Southern or Pacific coast is quite obvious, as may be seen from a glance at the table on the following page.

The rainfall, it will be noted, varies greatly owing to small local differences of environment, and includes at least one place far up on the world’s list of the wettest spots.

The stifling heat and damp of Greytown used to be well known to naval officers of the last generation, and it is probably a fortunate circumstance for their successors that the harbour has now so silted up as to be useless, for at one time it was frequently visited by our men-of-war.

The corresponding temperature records, given below, do not run very high, but the places on the Atlantic shore are extremely enervating on account of the extreme dampness of the air.

The West Indies.

—These islands are all under the influence of the north-east Trades, and enjoy a mild but rather moist climate, with comparatively little variation through the year. Nearly all of them are extremely healthy for places in the Tropics, although they are occasionally visited by devastating outbreaks of yellow fever.

The Americans have, however, proved in the case of Havana that it is quite possible to reduce the risk of this disease to a minimum by the adoption of appropriate measures against the mosquitoes that carry the disease, and it ought to be possible for any one, who takes the matter in earnest, to insure himself almost completely against this danger.

In the north, among the lesser Antilles, the Trade wind has an almost purely easterly direction. During the months from June to November terrific revolving storms, known as hurricanes, are of not uncommon occurrence and constitute one of the gravest drawbacks to cultivation, besides often causing much injury to life. So enormous is the force of the wind during these visitations that even objects of great weight and small surface are set in motion, it being an absolute fact that huge Admiralty anchors have been shifted from the position in which they lay in the dockyard at Port Royal in Jamaica.

It is unfortunately impossible, from considerations of space, to do more than give a few examples of the climatic conditions to be met with, but those selected may suffice to give a general idea of what may be expected, as no very great differences will be found, in spite of the large area over which these islands are scattered.

Jamaica, a table for which is given below, has a rather heavier rainfall of 70 ins. (1,778 mm.), but not so high as that of Martinique, 94·5 ins. (2,399 mm.), though even this cannot be considered high for a tropical climate. Of the other islands, Nassau in the Bahamas has 54·41 ins. (1,382 mm.); Port Au Prince, Haiti, 55 ins. (1,397 mm.); St. Croix, 46·56 ins. (1,183 mm.); St. Kitts, 51 ins. (1,295 mm.); Guadeloupe, 64·4 ins. (1,635 mm.); and Barbados, 57·74 ins. (1,467 mm.)—figures which serve well to indicate the general uniformity of climate throughout the group.

The table for Jamaica is as follows, but it must be remembered that most of the troops are now quartered at camps at a moderate elevation above the town, where it is considerably cooler than at the sea level.

Even Trinidad, the most southerly of all the islands in no way rivals the East Indies either in temperature or rainfall, the total of the latter being 65·5 ins. (1,663 mm.). Its hottest months, March and September, have a mean temperature of 78·5° F. (25·8° C.), and its coldest, February, of 75·4° F. (24° C.); the absolute extreme temperature of the year being 89·5° F. (31·9° C.) and 64° F. (17·9° C.). The highest temperature for any island is 100° F. (37·8° C.) at Havana, but from its landlocked position this place appertains more to the climatic conditions of the mainland than to the islands in general.

South America.

—The greater part of the tropical portion of the southern division of the western continent comes within the influence of the north-east Trades, which sweep up from the sea an enormous volume of watery vapour, which is precipitated gradually as the air current passes across the land. The second great factor in the determination of its climate is the position of the enormous mountain range of the Andes, quite close to the western coast, and of such a height as to cut off practically the last drops of moisture brought by the Trades, so as to leave the narrow belt of country between the Andes and the Pacific with a rainfall so scanty as to be in some instances almost negligible, as is the case with Lima, amounting to little more than an inch and a half in the year. So vast, however, is the amount of moisture imported by the Trades that the supply lasts out well, quite to the foot of the Andes, the rainfall of Manaos, half-way across, being rather greater than that of the east coast; but once the mountains are passed the change is abrupt and enormous. Unfortunately, however, when one sets one’s self to plot out the change as represented by a line of observations carried across the continent, one finds one’s self at once met by the difficulty that there is very little exact information to be obtained, as the all-absorbing interests of the ever-changing political barometer leaves the population little time to study the mercurial instrument, and they appear to be much fonder of playing with repeating rifles than with aneroids. Practically speaking, there is little exact information to be obtained for places at any distance from the coast, and on this account the tables given below refer almost exclusively to the littoral regions, and any attempt at anything beyond remarks of the most general character is out of the question.

Quite at the southern boundary of our limits we have the first-class observatory of San Paolo, which although but little outside the geographical, tropical zone, enjoys a temperature which shows that we are rapidly leaving warm climates behind, for the climate is already milder than most localities in the subtropical zone of the old world.