similar cause to that above suggested. These "meadows" are found along the coasts, wherever land is occasionally flooded by salt water.

(e) Alkaline Soils.—So much of the Far West is covered by alkaline plains that they here deserve notice. The soil is generally a light loam, sometimes clayey or sandy, containing but a limited amount of organic matter, but saturated with sulphates, carbonates, or chlorides of soda, potash, magnesia, and lime. These salts render the waters which they carry intensely purgative, and almost useless for domestic or manufacturing purposes. Little is known regarding the salubrity of these soils, but the fact that good water must either be pumped from a very great depth or transported long distances, renders their occupation improbable except in favored localities. Another unfavorable feature is experienced in the clouds of alkali dust blown about by the winds.

Geographically, alkaline soils are mostly restricted in the United States to the Great Basin-the valley lying between the Rocky Mountains and the Sierra Nevada. They extend over portions of Idaho, Utah, Wyoming, Nevada, Arizona, and New Mexico, and occupy regions formerly covered by extensive inland seas, which have now been mostly drained away by the cutting down of the river channels. The Great Salt Lake of Utah and other smaller bodies of alkaline water still remain.

(f) The Sea-shore Sands.-These form important soils, as they are uniformly healthful; and although for many reasons they are seldom selected for permanent habitations, their salubrity is unquestionable.

(g) Artificial Soils.-Under this heading we here include all deposits produced by artificially filling in low grounds. In laying out towns and villages, and the subsequent construction of streets and buildings, it generally becomes expedient to bring the surface of the ground to a certain degree of uniformity by removing the tops of hills and filling up the depressions, which are often marshy. This practice becomes particularly necessary in large cities, where land is very valuable. The objects generally sought by "filling in " are twofold: First, bringing the surface to a desirable grade; second, depositing material on a swampy place to "dry it up," and thus escape the expense of properly draining it. The latter object is usually only apparently attained, and is always done with the very great risk of producing subsequent sickness. The great mortality in certain sections of our cities is often directly traceable to mistakes made in preparing the soil for building, by this obnoxious practice, which cannot be too strongly condemned.

The areas of former swamps, and the channels of former streams, now covered up, are apparent in the relative health of people residing on ground formerly occupied by them, and that of the inhabitants of districts originally dry. All such places should be thoroughly drained before grading and building are begun, and the authorities should insist that these precautions be taken.

If it were not for the decidedly objectionable character of the filling generally employed, such soil might be less dangerous; but all kinds of waste matter and rubbish get mingled with the dirt, and a very unhealthy soil is the result. Besides this consideration, the mere filling up of a wet hollow does not effect any real drying or drainage, but rather lessens the possibility of the stagnant waters disappearing by evaporation; for the dirt becomes saturated with water, and this mixing with the organic portions produces a wet, nasty, almost invariably malarial soil, with no chance of effective drainage.

We do not protest against filling a naturally dry depression with a nat

urally healthy soil, and see no valid reason why it should be unhealthy. And even a soil charged with organic matter may ultimately become salubrious when used for this purpose, if deposited on a dry substratum, by oxidation and consequent removal of the organic matters contained; but we do not recommend this practice.

B.-INDIGENOUS SOILS.

These result from the decomposition and disintegration of rocks in situ, and their amount is constantly increasing, for reasons and by agencies already alluded to. The character of the rock from which they are derived determines their structure and composition, although their constituents are sometimes so much changed in the processes of decay, that chemically they may be essentially different from the original rock. Indigenous soils are greatest in amount in the non-glaciated parts of the country, where they form most of the superficial accumulations, but occur also to some extent, throughout all northern North America, wherever the Glacial Drift is thin or wanting. The presence of large quantities of Glacial Drift prevents or retards their formation.

The most important of these soils may thus be classified:

(a) Soils derived from Granite, Gneiss, Trap, Porphyry, and Feldspathic Rocks generally.-These are either stiff or loose clays, or loams, a true sandy soil rarely being formed from such rocks, and they are not to be regarded as highly salubrious, although the inclination of the strata may often give sufficient slope to the surface of the deposits to provide good drainage.

Soils produced from such rocks are found in patches along the eastern side of the Appalachian Mountain system (particularly from Western New Jersey, southward), in certain parts of the Rocky Mountain system and the Sierra Nevada, and elsewhere in the Far West. These feldspathic rocks are always associated with hilly or mountainous districts.

(b) Soils derived from Slates or Shales.-Clayey soils result also from the disintegration of these rocks, as they are mostly composed of this mineral, and are dangerous, unless the strata are sufficiently tilted.

Soils resulting from this source are found abundantly along the southern and middle portions of the Appalachian Mountains, and in many parts of the southern and central States and the Far West.

(c) Soils derived from Sandstones.-The breaking down of this rock produces sandy or loamy soils, clay never resulting from this source. These are very generally salubrious, unless rendered dangerous by local conditions of sewerage or improper disposal of refuse, which, it may be here remarked, will render the most desirable soil unhealthy. Such soils are so common south of the Glacial Drift, that no attempt at indicating their distribution need be made.

(d) Soils derived from Limestones or Marbles.-Calcareous soils result from the decomposition of these rocks, and almost invariably accompany them. Even when the rocks are overspread by other deposits, the soils are usually somewhat impregnated with lime.

Excepting the prevalent occurrence of hard waters, these soils are generally desirable, their drainage being good. They are widespread in distribution.

CLIMATOLOGY AND METEOROLOGY.

BY J. G. RICHARDSON, M.D.,

Professor of Hygiene in the University of Pennsylvania.

CLIMATOLOGY.

THE problem of furnishing a proper definition of Climate, abandoned as hopeless by Dr. Parkes in the body of this work, is to a certain extent solved by Prof. Loomis, in his excellent treatise on Meteorology, by the following description of what it is, and depends upon. "By the climate of a country we understand its condition relative to all those atmospheric phenomena which influence organized beings. Climate depends upon the mean temperature of the year; upon that of each month and each day; upon the maximum and minimum temperatures; upon the frequency and suddeĥness of the atmospheric changes; upon the transparency of the atmosphere and the amount of solar radiation; upon the moisture of the air and earth; upon the prevalence of fogs and dew; the amount of rain and snow; the frequency of thunder-storms and hail; the direction, force, and dryness of the winds, etc. All these particulars can only be determined by long-continued and careful observations."

The magnificent basis for a comprehensive system of American Climatology which is being rapidly laid, by the diligent observations in all parts of the country of our Signal Service Bureau, will doubtless afford us in the near future most important practical results; but as yet the chief triumphs of this valuable department have been gained in the science of meteorology, under which head they will be considered more in detail.

The study of climate has been especially aided in America by the observations tabulated in the admirable Isothermic maps (pp. 463, 464) for which we are so much indebted both to the Smithsonian Institution and to the United States Signal Office. The subject appears therefore to require a more detailed exposition than that given in the body of this book.

As Baron Humboldt in his "Cosmos" remarks, "If the surface of the earth consisted of one and the same homogeneous fluid mass, or of strata of rock having the same color, smoothness, density, and power of absorbing heat from the solar rays, and of radiating it in a similar manner through the atmosphere, the isothermal, isotheral, and isochimenal lines would all be parallel to the equator. In this hypothetical condition of the earth's surface the power of absorbing and emitting heat would everywhere be the same in the same latitudes.'

But as such is by no means the case, we find an infinite variety of temperature, humidity, and amount of rainfall existing at places upon the earth's surface at the same distance from the equator. Hence places having exactly the same latitude may possess widely different climates.

As observed by Surgeon General Hammond, "the climate of the United States is colder than that of European regions of the same latitude, but warmer than places similarly situated in Asia. Thus the fortieth parallel of north latitude passes through Philadelphia, and the forty-first runs a few miles north of Naples. The mean annual temperature of the former place is 54.57°, as determined from observations extending over six years (for twenty-four years ending 1876 the mean was 54.51°), while of the latter it was 62.06°, as deduced from observations continued through eighteen years. The fortieth parallel also passes through Pekin, but there the mean annual temperature is but about 52°."

Dr. Hammond thinks that the theories which seek to explain these remarkable variations on the ground that different proportions of the soil are under cultivation in Europe and America, are insufficient, and that the probable causes exist in the facts that the prevailing winds of Europe come from the Atlantic ocean, and being loaded with moisture, give out their latent heat as the vapor they carry with them is condensed into rain, and that the Gulf Stream, rushing out of the Gulf of Mexico heated to over seventy degrees, sweeps along the northern coasts of Europe and mitigates their frigidity. Moreover, Europe extends north to about the seventy-first degree only, and is then bounded by an open ocean; whereas the continent of America extends to the eightieth degree of north latitude, and is enclosed by a sea of ice. "From this region cold winds proceed, untempered by passing over any intervening water, and reduce the temperature of the whole of North America." Thus, for instance, the Isotherm, or Isothermic line of 51°, upon which occurs the same mean annual temperature of 51°, enters our Pacific coast high up near Vancouver Island, on the border of British America, crosses the continent in an irregular diagonal toward the Mississippi River near St. Louis, passes almost through New York, curves upward again toward the Arctic circle in the Atlantic, in consequence of the Gulf Stream, descends in Great Britain so as to pass nearly through London, traverses Russia near Odessa, China near Pekin, and Japan near Kanagawa.

As a general result of the investigations upon which isothermal charts are founded, we find that in the northern hemisphere, the west side of the continent is the warmer, and the eastern colder, although to this generalization a few exceptions are met with. Even in the island groups of the northern half of our globe, this rule generally holds good, the temperature of those upon the eastern coast being cold, whilst those upon the western coast are relatively warmer.

In the southern hemisphere the case is reversed, the eastern side of the continents being warmer than the western, so that the Isotherms which pass over South America and Africa, curve downward upon the map, that is away from the equator, in crossing these continents, in consequence of a mean annual temperature of 70°, for example, being found nearer the south frigid zone, upon the eastern than upon the western coast.

The appended Isothermic maps, copied by the kind permission of the Office from "Professional Papers of the Signal Service, No. 2," show at a glance the mean monthly temperature for January (winter), and for July (summer), during the ten years preceding 1881, for different portions of the United States.

They constitute some of the most important contributions to practical Hygiene yet furnished from the Signal Service Bureau, and being thoroughly accurate and reliable, will no doubt frequently aid our readers in judiciously directing invalids, especially phthisical patients, for whom they

are anxious to secure the potent remedial effects of removal to a more suitable climate.

In the United States the hottest portion is the southern end of Florida, and next to this rank Southern Texas, and Southwestern Arizona. The mean annual temperature of the whole country is not far from 53° F. The areas of territory having a mean annual temperature above 55°, comprise the entire cotton region, those above 70° the sugar and rice regions, and between 50° and 60° is included most of the tobacco region. As may be seen by consulting the accompanying Isothermic maps (pp. 463, 464), the cotton-growing sections lie between the Isotherms for July (the hottest month), of 75° and 85°, the winter limit of the cotton region being that of the Isotherm of 35° for January nearly. The regions ranging between 75° and 85°, average July temperature, appear to include all those portions which are liable to epidemics of yellow fever.

The coldest regions are found in the northern part of New England, Northern Michigan, Wisconsin, and Minnesota, and the high mountain region of the Cordilleras.

On the whole Atlantic coast from Penobscot Bay to the mouth of the Rio Grande, and the whole coast of the great lakes, besides a considerable portion of the Pacific coast, the highest observed temperatures range from 95° to 100°. The Atlantic plain stretching from the eastern base of the Appalachian system of mountains to the neighborhood of the coast, and nearly all of the Mississippi Valley, range in their highest summer temperature between 100° and 105°. This difference is, of course, due to the absence of any cooling influence from the Atlantic sea breezes.

The highest maximum temperature is reported from Southwestern Arizona, and from Southwestern California, where the thermometer is said to have registered 135° in the shade. The average maximum on the Pacific coast is lower than on the Atlantic coast, ranging between 90° and 100°, but at some distance inland in the great valley of California the elevated temperatures mentioned are met with.

The distribution of population in accordance with mean annual temperature, throughout the wide domain of our Union, is a question of much interest, and valuable light has been thrown upon it by recent bulletins from the Census office.

According to these Government statistics, it appears that ninety-eight per cent. of the total population of the United States reside in regions the mean annual temperatures of which range between 40° and 70° F.; eightytwo per cent. dwell in sections which have a mean annual temperature of 60° or under; sixty-nine per cent. in regions where the temperature is at or below an average of 55°; and thirty-eight per cent. inhabit portions of the country the highest mean annual temperature of which is 50°. From the same source we also learn that ninety-seven per cent. of our fellowcountrymen are exposed to summer heats which have a range of 20° only, lying between the mean temperatures for July of 65° and 85° F. This leaves a scattering fringe of population of only three per cent. outside of these limits, who suffer a more intense average heat or cold.

The brief but interesting statements of Professor Parkes in the text of this work, under the section treating of the effect of lessened pressure of the air as a climatic factor, and especially in its relations to Phthisis, may be appropriately supplemented here by some account of our own health resorts, which have been especially studied by American physicians in reference to that most fatal disease upon most of death registers of the Northern States-pulmonary consumption.