APPENDIX. The Board of Health, while generally approving the papers presented in this report, are not responsible for the particular sentiments expressed. BOARD OF HEALTH. THE CLIMATOLOGY AND DISEASES OF SOUTHERN CALIFORNIA. By H. S. ORME, M.D., President State Board of Health. TOPOGRAPHY. The territory to which this inquiry is restricted embraces the Counties of Santa Barbara, Ventura, Los Angeles, San Bernardino, and San Diego. It comprises an irregular outline extending about from latitude 32° 30′ to 35° 40′ and from longitude 37° to 43° 40′. In the direction of the parallels its extreme width is three hundred and thirty miles, and its extreme length two hundred and thirty miles. Its coast line, following the indentations, measures about three hundred and thirty miles. Four of the five counties have a wide exposure to the sea; and but one of the five, viz.: San Bernardino, is entirely inland. Two thirds of the coast line of Santa Barbara County, and about one half of that of Los Angeles County, presents a southerly exposure. The remaining portion of the entire coast line faces westerly or southwesterly. Between the most easterly point on the coast and the most westerly there is a distance of two hundred and fifteen miles. The western part of this region is traversed by low ranges of mountains, having an average altitude of from three thousand five hundred to six thousand feet. A few of the higher peaks exceed seven thousand feet in altitude; the culminating peak, Mount San Bernardino, reaches to a height of eleven thousand eight hundred feet above the sea level. These mountain ranges inclose a number of small but fertile valleys, a few of which are settled. All of them are capable of supporting a population of moderate density. The eastern portion consists of an arid and tolerable level tract, usually called the Mohave Desert. A small portion of this in the extreme southern part of the State is known as the Colorado Desert. It is separated from the former by a few isolated ridges which form the southern remnant of the San Bernardino Mountains. The western part of this arid region has an altitude of two thousand feet, the central and eastern parts are much lower, and in several places are below the sea level. Two of these depressions, Death Valley, and the sink of the San Felipe River, are about four hundred feet below the sea. The lowest point on the Southern Pacific Railroad through the Colorado Desert is twenty-six miles east of Indio, or five miles west of Dos Palmas; this is two hundred and sixty-six feet below the sea level. From this point the ground falls off south, until reaching a point half a mile distant, the level bottom of the desert in the form of a salt bed is found; this is two hundred and eighty feet below the sea. This is where the "New Liverpool" salt company are operating, and have their works. But by far the most important part of Southern California is the western slope of the Coast Range of mountains, which, from a narrow strip in the north, widens to a broad plain n the south. Its area is materially increased also by the valleys of numerous short rivers which traverse the mountain ranges, and flow towards the ocean. This region is possessed of wonderful fertility, and is capable of supporting a denser population than any other part of California. The conditions of soil and climate are such, that it will produce almost any crop that can be grown between the latitudes of Lake Manitoba and Key West. It is this region which we shall chiefly consider in speaking of Southern California. Its hoard of grain already contributes to feed the overcrowded population of London; its preserved fruits are sold in the cities of Southern Italy. SOIL. There are many varieties of soil to be found in the southern counties of California. These in their bearing upon the climate of the region may be classified with respect to their retentiveness of moisture. The non-retentive soil includes the red and blue clays, of which there are but little, and the well known adobe. The latter is more or less abundant, occurring in irregular patches from a few acres to several square miles in extent. The retentive soils comprise the gravelly loams, the micaceous sediments, and the so called sand bottoms along the river courses. This classification may seem at first paradoxical, but facts are stronger than theory, for while the wet and boggy clay and adobe bakes under a semi-tropical sun into a friable and perfectly dry mass, the sands and more porous soils are moist throughout the year. This peculiarity, which is due to capillarity, is not only an important element in insuring great productivity to the soil, but it also exerts a decided effect in moderating the severity of the Summer's heat. The soil of the eastern part, or the arid region, and also the detritus brought down by the rivers during the Winter floods, is commonly called "sand." Of true sand, however, there is not a particle, excepting along the coast. The alleged "sand" is nothing more than disintegrated granite rock, rich in feldspar, and containing a notable quantity of mineral phosphates. This is the secret of the wonderful productiveness of the soil wherever watered; it is also a most important factor in determining the fine quality of the fruit and vintage, for which Southern California has already a world-wide reputation. HUMIDITY. Under this head we will consider the annual rainfall, and independently the amount of moisture present in the atmosphere. A knowledge of the total rainfall of a region gives but little insight as to its climatic conditions; the distribution of the rainfall reveals much. In Southern California, as on the Pacific Coast generally, the rainfall occurs almost wholly during the Winter months. A few scattering showers occur in November and December; heavier rains fall during the following three months, especially during February and March. There are occasional rains in April, and rarely in May. In the mountains, however, there are at times heavy mists, and even dashes of rain. The average rainfall of the southern part of the State may be seen from the following table. Of the five stations mentioned, Santa Barbara and San Diego are on the coast; Los Angeles is about seventeen miles inland. San Bernardino, about sixty miles inland. Yuma is situated in the heart of the arid basin region, the town is just over the line in Arizona (old Fort Yuma is in California). In general the rainfall of the western part of Southern California is sufficient to produce as much as the soil will stand without "wearing out." This on the average will hold good six years in seven. In the eastern region, wherever water can be obtained for irrigation, vegetation grows with wonderful luxuriance, as may be seen in the case of the railway station at Indio, in the Colorado Desert. Without artificial irrigation, scarcely anything beyond a few species of cactus and agave will grow. From the preceding it will be seen that the habitable portions of Southern California receive but a trifle less of rain than the lower Sacramento Valley, and considerably more than the San Joaquin Valley. * A more important factor than the rainfall, is the relative humidity of the air. This is a matter somewhat difficult to present, as the atmosphere may be extremely "moist" one day, and very "dry" on another, and yet in both cases contain exactly the same amount of aqueous vapor. The cause, it is hardly necessary to state, is due to a difference in temperature. In the one case the air, because of its low temperature, contains nearly or quite all the vapor it can possibly hold. In the second case, while the air may contain the same amount or even more of moisture, the air seems dry, because its high temperature enables it to hold three or four times as much vapor as it appears to contain. In Southern California the seasons of dry air and moist air are well marked. Aside from these there are belts of country especially liable to heavy fogs. From the time of the first rains, the belt of country next the coast is bathed in an atmosphere which is tolerably moist. At a distance of a few miles inland the relative humidity increases-not because there is more moisture but because the temperature is apt to range lower. Here the fogs are heaviest and the deposition of dew is greatest. Beyond this belt as the distance from the coast increases, the relative humidity decreases, until, at the crest which separates the Pacific Slope from the Great Basin, the air throughout the year is dry, pure, and invigorating. During the Summer months the relative humidity is much less than in Winter. The deposition of dew ceases altogether, and the atmosphere becomes very dry. There is no decomposition of organic matter, because there are no Summer rains. As a result, the atmosphere is so pure and free from organic germs, that meat exposed to the air cures or "jerks," but does not putrify. In the Colorado Desert, and even in the high mesa lands west of the divide, culture fluids, such as are used in cultivating bacteria, if properly sterilized, often evaporate without "breaking down." It must be borne in mind, however, that this condition, although a prevalent one, is by no means universal. There are many days during the rainy season when the atmosphere is damp, chilly, and depressing. There may also be occasional localities where on account of excessive irrigation and imperfect drainage, etc., the atmosphere is liable to be unwholesome, and malarial diseases might prevail. Damp and chilly days, however, are rare even in Winter, * Sacramento, 19.7 inches; Stockton, 16.7 inches; Visalia, 9 inches. |