so vitiated by the density of the population and other causes, the effect of the air of the coast is well known to be beneficial and restorative, in an eminent degree. The amount of the stimulant action of the saline atmosphere is apt to be greater, in proportion as the air that has been breathed habitually, is more moist, dense, and relaxing. And accordingly, circumstances which might justify removal from an inland, upland, or mountainous situation, to the sea-coast, or from an open and pastoral, or even from a well-drained and rural district,-might not justify such removal from a low, damp, rural district, or from the inefficiently drained and badly ventilated districts of the towns.

There is an observation of much practical value, that has been too little attended to, in the practical adaptation of the great hygienic fact of the stimulant air of the sea-coast. The influence of the saline impregnation of the air extends inland for several miles,-gradually becoming less and less considerable, until it ceases to obtain, in an evident degree, from ten to twenty miles inland; unless when a high wind blows from the sea-ward, when the saline matters may be shown to be present in the air, by means of chemical reagents, to a greater distance inland than even twenty miles. The tempering and equalising effect of the sea on the temperature and climate of a country extends very much farther than this: so much so, as to modify the whole climate of Europe, and other equally broad peninsulas. What is now referred to, is, especially, the stimulant action of the sea air from its saline impregnation. It follows, that, with

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some care and trouble, the degree of stimulant action that a case requires, may sometimes be secured by a location, that is nearer to or farther from the coast; the distance inland being usually greater, when the prevailing winds are strong and from the sea-ward; and less, when the elevation above the level of the coast is greater, or when the sea breezes are more or less intercepted by the intervention of higher grounds, or of woods and plantations.

The effect of the air of the sea-coast, and of insular situations generally, is much influenced by the nature of the soil, the character of the prevailing vegetation, the dryness or dampness of the atmosphere, the latitude of the place, &c. The air of the coast near the embouchures of rivers, which overflow their banks during the rainy seasons, leaving extensive marshy lands to dry in the intervals between the rains,-especially if the soil be alluvial, and the vegetation rank and abundant, and the temperature high,—must be much more destructive to health, than inland situations, which are probably on a higher level, and watered with streams of a less considerable size, and in which there is consequently less risk of extensive inundations, and of miasmatous exhalations to a correspondingly large degree.

The single circumstance of the necessary humidity of the air near the sea, independently of its equalised temperature, and its saline impregnation, must influence, to a very important extent, its effect on health and disease; and more particularly in countries characterised by long periods of drought,-the

inland atmosphere of which is necessarily and singularly dry, the land during the long droughts being quite bare of all vegetation,-and the soil being loosened, from lack of moisture, into the condition of a fine, penetrating, and irritating dust. But, even in the districts of higher latitudes, and more uncertain and watery skies, the effect of the humidity of the air near the coast must be far from inconsiderable on some morbid conditions; and in many cases may be of important character,-as when there is a decided deficiency of secretion in the bronchial tubes, in cases of chronic pulmonary affection; and might be selected for the temporary or long-continued residence of the invalid, under such circumstances, with much chance of benefit.

The nature of the soil and the geological character of a district influence, in an important degree, its sanatory condition. Its drainage and vegetation, and the character of the air which passes over it, must be thus affected to a great extent; and the health of the population, and the effects of the air on disease, be largely influenced. Whether the surface of the district be formed principally or essentially of the primary rocks, or of mountain-limestone, or of sandstone, or of clay, or of alluvial matters, may be readily conceived to constitute influential circumstances in modifying the condition of the air, as to its dryness, and its freedom from possible sources of impurity. But, besides these more evident and explicable differences, it is probable that the surfacestratum or the surface-soil of a district may directly

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influence the character of the atmosphere, to an extent favourable or otherwise to different constitutional conditions, or different states of disease. Living in a district in which the mountain-limestone very extensively prevails, it often happens to me to be assured by invalids, especially those who suffer from different forms of rheumatism, that they experience a perceptible degree of palliation of their sufferings, and at all events a perceptible improvement in their general health and feelings, when they arrive within the influence of the limestone air; and they have repeatedly assured me, they could readily distinguish the air of such a district by the smell.

In connection with this subject, the very different physical conditions, and the very different effects on health and disease, of the air of hills and that of valleys, may be fitly adverted to. The extraordinary influence of valleys on the health: an influence so much greater than could have been pre-conceived is probably ascribable, in a great degree, to a deficiency of ventilation on the large scale, and to the comparatively stagnant and unchanged atmosphere. The effects of this on the physical condition of a population are often so great, that other means of accounting for such consequences have frequently been advanced: the true explanation appearing to be, however, that (neither the peculiar character of the water made use of by the inhabitants, nor the nature of the soil, nor the employments, nor the clothing, nor the dwellings, nor the habits of the people, helping to a satisfactory rationale of the effects, inasmuch as such effects do not extend beyond the valleys,

although such several circumstances equally obtain in the adjoining localities) the stagnant atmosphere is the single cause of a degree of morbid degeneration, that seems to be proportioned to the degree in which the air is left in such a state of quiescence. The fearful accounts of cretinism, in all the appalling detail of idiotcy, demoralisation, and extreme physical wretchedness, seem to confirm this view to the fullest extent.

Besides this most influentially important condition of the air of valleys,-which may obtain to a greater or less degree, from the point at which it occasions cretinism in the worst type, to that which is not perceptibly detrimental to the health of the population,— the atmosphere of valleys is usually characterised by a somewhat higher temperature, and by a more uniform temperature, than the air of plains of the same elevation, and in the same latitude. The air of valleys is usually more humid in its character than that of the plains. This may be usefully considered, in selecting a place of residence for special cases of disordered action.

The effect of the prevailing winds that blow over a district (as to the direction from which they blow; the tract they may have passed over, more or less remotely,—such as snow-capped hills, or arid plains, or a vast ocean, and the consequent temperature, humidity, &c., of the air) is very great, not only in raising or lowering the temperature of the atmosphere, but in producing or removing mists and clouds, in diminishing or increasing the amount of the radiation from the earth, in influencing the electrical