character when present, is respectively modified by tempe rature. The theory of the coincidence of certain temperatures with the occurrence of certain diseases, applies equally well to the doctrine of the chemico-pathological agency of heat in the production of miasma, and in the susceptibility of the human system to its action-whether miasmata are considered to be of chemical origin from decaying vegetation, or to be marsh-nurtured animalcula infesting the air, or as Dr. Willis and Mr. Daniel, who are now investigating the diseases of Western Africa, believe, malaria and the unhealthfulness of the intertropical climates, results simply from the heat combined with moisture-in other words, from moist warm air,—as in either case heat is equally necessary to the presence of each of these pestiferous agents. The yellow fever has never yet occurred in our latitude except in a season of unusual heat. It is stated that in every instance when it has occurred in Philadelphia, the mean temperature has been for three weeks previously not less than 79 degrees. The endemic diseases of the equatorial parallels are found to extend themselves with the more vertical sunlight toward the tropics, and diseases analogous to the yellow fever of tropical latitudes (whether endemic or propagated by contagion,) are likely to appear whenever the intense heat of summer produces, for the time, tropical temperatures in the more temperate parallels. As we find the yellow fever in summer occurs at Havana on latitude 23 north usually," at New Orleans on the 30th frequently, at Charleston on the 33d less frequently, and sometimes, though very rarely, at Philadelphia and New York cities of the 40th parallel-but disappearing in all instances with the return of frost, so we find that the catarrhal and pulmonary diseases of cold parallels are apt to appear during the winter of more southern skies. These diseases occur when, in fact, those temperatures are present which are productive of the peculiar diseases of the north, and thus the winter and summer of the temperate zones subject their inhabitants alternately, to some extent, as the temperature alternates, to the diseases of tropical and arctic latitudes. If man could migrate like the birds it would be often essential to his health, and it is common to find invalids fleeing at the approach of winter to warmer climes, and to find the inhabitants of southern regions avoiding the ardent heats of summer by a sojourn at the north, or amid the breezes of the ocean; but it is easier for man to mitigate the rigors of a cold climate than to moderate the heats of the tropics. A favorable change of wind may for the time, and in degree, ameliorate the climate and produce the relief which is sought for when the pulmonary invalid seeks a southern clime, or the heat-enfeebled and feverish patient betakes himself to the cooler air of the sea side or of the mountains. The influences which climate, the fact of proximity or remoteness from the temperate latitudes, either toward the torrid or frozen regions of the earth, exert on the health and physiological condition of man, deserve, among innumerable other facts of every locality, a very careful arrangement. According to Monsieur de Jonnés, of the Institute of Paris, the average annual mortality of the natives of the torrid zone may be stated at one in 25 or 27 individuals— while the average mortality of the most healthful countries of the temperate zones is only one in 58 or 59 persons; by which it appears that the chances of life in temperate climates are considerably more than twice greater than under the blazing sun of the tropics. This result is caused partly by the fact already stated, that it is easier to protect ourselves artificially from cold than heat. The climates he found most favorable to the prolongation of human life, are those of the northern portion of the temperate zone of peninsular Europe, where the temperature is comparatively cold and even rigorous, generally, but still modified in winter by the Gulf Stream current of the Southern Atlantic. The ocean breeze is healthful in all climates, but it is remarkable that the humid atmosphere of the ocean in northern latitudes should be the most congenial of all others to human longevity; accordingly, islands have remarkable healthfulness. The climate of the British isles, of cold and foggy and mountainous Scotland, and the maritime countries in the vicinity of the Polar circle-Sweden and Norway and Iceland-appear to insure the longest period to human existence. In warm climates, the chylopoietic diseases, the bilious fevers which accompany the miasma of decaying vegetation-the whole class of maladies which affect the digestive organs, derive great activity, probably from causes analogous to those chemical laws by which increased temperatures hasten the universal tendency to putrefaction-while in cooler climates these diseases are comparatively unknown; and pulmonary diseases, those infirmities to which the delicate organization of the lungs is liable, increase as we approach the variable latitudes, and become the most destructive on the bills of mortality in the temperate zones. The mortality of warm climates is always much greater to strangers than to acclimated and native residents-thus in Batavia the observed mortality of Europeans is one to eleven, while to natives it is not much above the average mortality of tropical countries. The healthfulness of countries, of districts, of cities, is varied greatly of course by civilization, modes of life, and a thousand causes; but the great influence of temperature exhibits itself in every country, in every race, and under every degree of civilization. The chances of death are one half greater on the smiling plains of Italy, or under the beautiful skies of Greece, than in uncivilized Russia, or amid the frozen fields of Iceland. At a recent meeting of the British Statistical Society, a paper was read on the means of forming and maintaining troops in health, the author being Mr. Balfour, an Assistant Surgeon in the Madras army. A London journal, alluding to the matter, says: "The inhabitants of towns are the individuals whose position most closely approximates with that in which troops are placed; and the mortality among the inhabitants of towns in the prime of life is nearly one-third greater than among the rural population. In comparing, therefore, the mortality of military life, it becomes necessary to take for the standard the average of those towns in which the troops are quartered. The deaths among the foot guards amount to 21.16 per thousand annuallý, and 16 per thousand may be fairly received as the average of the civil inhabitants of Britain. We thus obtain a standard by which to contrast the loss of life in Britain, with that to which our armies are subject when serving in foreign countries.” The following is the result of Mr. Balfour's researches:— This table, of course, relates to healthful men in the prime of life. An. mor. per 1000 Mauritius Bermudas St. Helena According to the best authorities there annually dies in the Roman States of Italy, and in the pagna. Of the whole population, In Italy and Greece 1 in 28 persons 1 in 30 - 483 marshes of the Cam If the temperate zones of latitude are undeniably important to the health of their inhabitants-the comparative local healthfulness of local districts cannot be too carefully |