35- 



NA TURE 



\ August 7, i! 



totil change in the daily habits of life, have assisted in the 

 beneficial results. The diminution in the quantity of air. and 

 c-msequently of oxygen, taken in at each breath is to a certain 

 extent c mnterbalanced by an increased frequency and depth of the 

 respirations, and a greater capacity of the chest. In this country, 

 alterations in the liar, .metric pressure are chiefly valuable as 

 indicating an approaching change in the wind, and as well as of 

 the amount of moisture in the air ; hence the instrument is often 

 called "the weather glass." A sudden diminution in the 

 atmospheric pressure is likely to be attended with an escape of 

 ground air from the soil, and therefore to cause injury to health, 

 especially among -t the occupants of basement rooms, unless the 

 whole interior of the building he covered with concrete. 



Temperature. — Experience has shown that man can bear 

 greater variations of temperature than any other animal, as in 

 the Arctic regions a temperature of 70 degrees Fahrenheit, or 

 more than 100 degrees below freezing-point, can be safely borne ; 

 that he can not only live but work, and remain in good health 

 in these regions, provided that he be supplied with suitable 

 clothing and plenty of proper food. On the other hand, man 

 has existed and taken exercise in the interior of Australia, when 

 the thermometer showed a temperature of 120 degrees Fahrenheit, 

 or nearly 90 degrees above freezing-point, so that he can live and 

 be in fairly good health within a range of nearly 200 degrees 

 Fahrenheit. 



The effects of a high temperature vary very much according 

 to the amount of moisture in the air, as when the air is nearly 

 saturated in hot climates, or even in summer in our own, more 

 or less languor and malaise are felt, with great indisposition to 

 bodily labour. With a dry air these are not so noticeable. The 

 cause is evident ; in the former case but little evaporation 

 occurs from the skin, and the normal amount of moisture is not 

 given off from the lungs, so that the body is not cooled down to 

 such an extent as by dry air. .Sunstroke is probably the result, 

 not only of the direct action of the sun's rays, but partly from 

 diminished cooling of the blood by want of evaporation from 

 the lungs and skin. 



The effects of temperature on man does not depend so much 

 on the mean for the day, month, or year, as on the extremes, 

 as when the days are hot and the nights comparatively cool, the 

 energy of the system becomes partially restored, so that a 

 residence near the sea, or in the vicinity of high mountains, in 

 hot climates is, other things being equal, less enervating than in 

 the plains, as the night air is generally cooler. It is commonly 

 believed that hot climates are necessarily injurious to Europeans, 

 by causing frequent liver derangements and diseases, dysentery, 

 cholera, and fevers. This, however, is, to a certain extent, a 

 mistake, as the recent medical statistical returns of our army in 

 India show that in the new barracks, with more careful super- 

 vision as regards diet and clothing, the sickness and death-rates 

 are much reduced. Planters and others, who ride about a good 

 deal, as a rule keep in fairly good health ; but the children of 

 Europeans certainly degenerate, and after two or three 

 generations die out, unless they intermarry with natives, and 

 make frequent visits to colder climates. This fact shows that 

 hot climates, probably by interfering with the due performance 

 of the various processes concerned in the formation ami 

 destruction of the bodily tissues, eventually sap the foundations 

 "f life amongst European-.; but how far this result has been 

 caused by bad habits as regards food, exercise, and self- 

 indulgence, I cannot say. Rapid changes of temperature in 

 this country are often very injurious to the young and old, causing 

 diarrhoea and derangements of the liver when great heat occurs, 

 and inflammatory diseases of the lungs, colds, &c, when the 

 air becomes suddenly colder, even in summer. 



The Direct influence of rain on man is not very marked in 

 this country, except by giving moisture to the air by evaporation 

 from the ground and from vegetable life, and by altering the 

 level of ground water. This is "a subject almost overlooked by 

 the public, and it is therefore as well 'that it should be known 

 that when ground water has a level, persistently less than five 

 feet from the surface of the soil, the locality is usually unhealthy, 

 and should not, if possible, be selected for a residence. 

 Fluctuations in the level of ground water, especially if great and 

 sudden, generally cause ill-health amongst the residents. Thus, 

 Dr. Buchanan in his Reports to the Privy Council in 1866-67, 

 showed that consumption (using the word in ils most extended 

 sense) is more prevalent in damp than on dry soils, and 

 numerous reports of medical officers of health, and others, which 

 have been published since then, show that an effective drainage 



of the land, and consequent carrying away of the ground water 

 has been followed by a diminution ofthese die. 



Varying amounts of moisture in the air materially affect the 

 health and comfort of man. In this country, however, it is not 

 only the absolute but the relative proportions of aerial moisture 

 which materially influence mankind. The quantity of aqueous 

 vapour that a cubic foot of air can hold in suspension, when it is 

 saturated, varies very much with the temperature. Thus at 40 

 degrees Fahr. it will hold 2 - 86 grains of water ; at 50 degrees, 

 4 - io grains; at 60 degrees, 5 '77 grains; at 70 degrees, 8"OI 

 grains ; and at 90 degrees as much as I4'85 grains. If saturation 

 be represented by 100, more rapid evaporation from the skin 

 will take place at 70 degrees, and 75 per cent, of saturation, 

 than at 60 degrees when saturated, although the absolute quantity 

 of moisture in the air is greater at the first-named temperature 

 than at the latter. As regards the lungs, however, the case is 

 different, as the air breathed out is, if the respirations be regular 

 and fairly deep, completely saturated with moisture at the 

 temperature of the body. In cold climates the amount of 

 moisture and of the effete matters given off from the lungs in the 

 expired air, is much greater than in hot climates, and the body 

 is also cooled by the evaporation of water in the form of aqueous 

 vapour. Moist air is a better conductor of heat than dry air, 

 which accounts for much of the discomfort felt in winter when a 

 thaw takes place as compared with the feeling of elasticity 

 when the air is dry. In cold weather, therefore, moist air cools 

 down the skin and lungs more rapidly than dry air, and colds 

 consequently result. London fogs are injurious, not only on 

 account of the various vapours given off by the combustion of 

 coal, but in consequence of the air being in winter generally 

 saturated with moisture at a low temperature. The injurious- 

 ness of fogs and low temperatures will be presently dwelt upon 

 at greater length. 



Variations in the pressure and temperature of the atmosphere 

 exert a considerable influence on the circulation of air contained 

 in the soil, which is called ground air. As all the interstices of 

 the ground are filled with air or water, the more porous the 

 soil, the greater is the bulk of air. The quantity of air contained 

 in soil varies very much according to the material of which the 

 soil is composed, as it is evident that in a gravelly or sandy soil 

 it must be greater than when the ground consists of loam or 

 clay. The estimates vary from 3 to 30 per cent., but the latter is 

 probably too high. If, therefore, a cesspool leak into the 

 ground, the offensive effluvia, if in large quantities, will escape 

 into the soil, and are given off at the surface of the ground, or 

 are drawn into a house by the fire : but. if small, they are ren- 

 dered inocuous by oxidation. The distance to which injurious 

 gases and suspended or dissolved organic matters may travel 

 through a porous soil is sometimes considerable, as I have 

 known it pass for 130 feet along a disused drain, and above 30 

 feet through loose soil. 



Winds exercise a great effect on health both directly and in- 

 directly. Directly, by promoting evaporation from the skin, 

 and abstracting heat from the body in proportion to their dry- 

 ness and rapidity of motion. Their indirect action is more im- 

 portant as the temperature and and pressure of the air depend to 

 a great extent in their direction. Thus winds from the north in 

 this country are usually concomitant with a high barometer and 

 dry weather ; in summer with a pleasant feeling, but in winter 

 with much cold. South-west winds are the most frequent here 

 of any, as about 24 per cent, of the winds come from this 

 quarter against 1 64 from the west, ui from the east, and the 

 same from the north-east ; loi from the south, 8 from the north, 

 and a smaller number from the other quarters. South-west 

 winds are also those which are most frequently accompanied by 

 rain, as about 30 per cent, of the rainy days are coincident with 

 south-west winds. Another set of observations give precisely 

 the same order, but a considerable difference in their prevalence, 

 viz. south-west 31 percent., west 14J, and north-east Il4 per 

 cent. Easterly winds are the most unpleasant, as well as the 

 most injurious to man of all that occur in this country. 



1 now propose discussing very briefly the known relations 

 between meteorological phenomena and disease. I say the 

 known relations, because it is evident that there are many un- 

 known relations of which at present we have had the merest 

 glimpse. For instance, small-pox, while of an ordinary type, 

 and producing only a comparatively small proportion of deaths 

 to those attacked, will sometimes suddenly assume an epidemic 

 form, and spread with great rapidity at a time of year and under 

 the meteorological conditions when it usually declines in fre- 



