THE SANITARY AGENCY OF WINDS.

Globe, Volume IV, Issue 453, 26 November 1875, Page 3

THE SANITARY AGENCY OF WINDS.

(From the A nstralasian,)

The important and interesting subject of the sanitary effects of winds in hot climates is verv ably discussed in an article in a late number of' the llevuc des Deux Mondes which is founded on a work by Dr Pauly, entitled ''Climates and Endemics." It is rightly said that it is only recently that the science of public hygiene has been able to get firm foothold, and indeed the more general science of meteorology, which is its true foundation, is itself only a science of very recent date. For ages there has been in the popular belief a close association between warmth of temperature and insalubrity of atmosphere. From the fact that many tropical regions are the enduring home of fever malaria, a rough generalisation has been made attributing the disease to the single condition of climate. But it is very well known that some tropical regions are perfectly healthy, and absolutely free from diseases of an endemic character. It becomes therefore a matter of supreme importance, especially in a new country, where the choice of site for a settlement is a practical problem that often has in some way or other to be solved, to investigate what are the conditions upon which what may be called atmospheric salubrity depends, and by which it is influenced. This subject has been carefully explored by Dr Pauly, and his deductions are placed before us in a clear and distinct form in the article under notice.

The conclusion to which inquiry leads appears to be that the freedom from malaria of a district in a hot climate depends upon its being swept by fresh breezes, and these again depend upon various conditions, and especially upon the topographical conformation of the locality. " Broad plains and extensive plateaux are generally very healthy ; many mountainous islands in the tropical zone are also healthy, where the mountains form a great central mass more or less rounded up into a cone. On the other hand, narrow littoral plains, walled on one side by the crests of a coast range, as, for instance, the Brazilian coast from Bio to Bahia, or the Atlantic shores of Central America, are regions infested by malaria. The same remark applies to certain islands, barred aloug their whole length by a rampart of high mountains, as Madagascar, Java, and Sumatra, when these mountains, in place of being parallel to the prevailing winds (trades or monsoons), stand across the course of these currents." Where a coast line like that of the Mediterranean has ridges of mountains running down to it, and dividing the low coast country into a series of fertile basins, each watered by its little river ; these are almost always unhealthy. "In each of these little basins," says M. Pauly, " sprang up, as in a prolific soil, autonomous political societies, republics jealous of their independence ; it is in them that flourished the cities of Sparta, Smyrna, and Tarsus, so prosperous and so rich ; and yet in all of those concavities malaria has been a permanent obstacle, an enemy at times kept under, but always alive and ready to resume host'lities. . ; . This endemic, reduced almost to nothing by the skilful agriculture of the ancients, reappeared in all parts of the coast of the Mediterranean as a consequence of the invasion of the barbariaus of the fourth and fifth centuries, and especially subsequently to the Mussulman conquest of the seventh and eighth centuries." It is remarked that the great and special endemics [hot countries—fevers, intermittent or remittent, fevers of malaria, cholera, yellow fever— ap pear to observe a geographical distribution something similar to that of th« various vegetable tribes. At certain places we see them frequent and heavy. In this way the enormous trees of the tropical forest are found in Brazil. In other parts they are rarer and less serious, exactly as we see the forest thiu out on the edges of the plains, where trees give way to graceful shrubs and bushes. And in some privileged places in warm countries those maladies disappear altogether for long periods of years. Although surrounded by a luxurious vegetation and separated only by a few miles from hotbeds of malaria, the traveller, on reaching one of these oases, is as though sheltered in a safe harbor. In fact these epidemics do not extend as an unbroken mantle over vast regions; they are divided into narrow strips, which often have between them uninfected areas of considerable extent, and even in the most insalubrious regions there are found what may be looked upon as isles of refuge, which are almost perfectly free from the poison. Dr Pauiy, during his residence in Algiers, made some curious observations of the singularly local character of these influences, and the same remark has been made by travellers in many malarious tracts of the world's surface. The combination of tropical heat and abundant rains, which stimulate into growth so luxuriant a vegetation in the latitude of Central America, is certainly recognised as a chief condition of insalubrity of climate, and the fearful character of the epidemics which visit those countries is well known. As illustration, it may be mentioned that the fever-smitten atmosphere was one of the chief obstacles to the formation of the Panama Bail way, which is said to have cost a life of a man for every sleeper>n the line. And yet in the neighbouring sea are found certain islands where, in spite of these unfavorable climatic conditions, the healthiness of the air is perfect and incontestable. On the other hand, travellers have found in the Peruvian Andes, at the bottom of gorges, and in the depth of narrow valleys, localities which, in spite of an altitude of 10,000 feet, were hotbeds of malaria.

The only explanation of these enigmas is that the focus of miasma is always an enclosed basin where the shape of the ground produces a stagnation of the atmospheric strata, while the points of exceptional salubrity are those which are always swept by winds. The guarantee of a favorablesituation is its relative height, or the fact thai it cannot be dominated by localities in th< vicinity. This is the indispensable condition of free access of the wiuds. This relative altitude, which gives security against the endemics caused by miasma, need not be a very considerable absolute height, The Polynesian and Australasian archipelagos exhibit a crowd of islands of merely sea level, which are of a wonderful salubrity, because the trade winds or westerly winds

blow across them every day in the year. Some of these islands have central mountains, but these do not check the free play of the winds, which in the southern seas have so remarkable a strength. Says the article we have under notice : "The great importance of the part which devolves upon the wind of purifier of the atmosphere becomes especially sensible by observing the contrasts presented by regions apparently placed in identical climatic conditions. In both regions we may find tropical rains, virgin forests in which the trees are matted together by a network of creeping plants, a deep soil enriched by the decomposition of old tree-trunks and herbaceous plants, a sun hot enough to ripen coffee, sugar, and cocoa ; and yet on oue side fevers and cholera reign as on the islands and shores of the Bea of the Antilles, while on the other we have the delicious and invigorating climate of the South Sea Islands." A like comparison may be made between many cor-respondingly-situated parts in the northern and in the southern hemisphere, and it will be found that the great superiority in point of healthiness enjoyed by the southern is due to the fact that the predominant winds are much more constant and more powerful than those of the northern hemisphere. When malaria is found on the South, it is found either at " centres of aspiration" or calm zones, as at Java and North Australia, or where obstacles such as chains of mountains exist to the sweep of the wind, as, for instance, in Madagascar. The whole of the vast surface of Australia appears to be highly salubrious till we get within the tropics, where we find malarious marshes, but we are then in the calm zones and areas of upward movement |of the air, and the purifying effect of regular strong breezes is absent.

These observations go to show the importance, in choosing the place for a settlement, of paying heed to the conformation of the site, the proximity and direction of the nearest chain of mountains, and, above all, the character and regularity of the prevailing winds. In the southern regions of Australia we can hardly go wrong, the atmosphere being always in a state of movement, by which all noxious exhalations are swept away as soon as formed. But it is evident that in the north of the continent the circumstances are very different, and wisdom dictates that, in selecting sites for towns, not only the economical and commercial, and the specially local sanitary conditions, but those larger and even more essential ones should be taken into serious consideration.