Imatges de pÓgina

appearance 3,000 or at most 5,000 years along the course of streams and on ago. The bay-tree is next in priority of springy hill - sides, but it will accommoage. Like the redwood, it propagates date itself to almost any locality. Its itself from saplings thrown out from the pungent aroma fills the atmosphere withperiphery of the stumps of its decayed out its circumference, and doubtless it ancestors. I have never seen any of exerts an anti-malarial influence as powthe old stumps exceeding eight feet in erful as the eucalyptus, or any other tree diameter, and from imperfect data I am which has gained a real or factitious repinclined to limit their age to 800 years. utation in this respect. Our evergreen oak comes next. The It has not been proved, though assertoldest tree which I have seen in this ed until belief is established, that the district has not exceeded 500 years. aroma of the eucalyptus is effective in From the sparseness of vegetable mold preventing the incubation of intermitand from the absence of any relics of tents. The exceedingly rapid growth of former generations, it can not be claim- the tree is dependent on the quantity of ed that it has been growing on our en- water which is accessible to its roots. cinal for more than 1,000 years. These The proverbially unhealthy atmosphere estimates may be regarded as being of swamp- land is due to stagnant wapurely hypothetical, but they are no ter. Where currents are established by more so than the bases which refer the drainage or by excess of water, the cause origin of man to remote antiquity. If of malarious fevers, if not entirely rethe character of strata in which organic moved, is materially abated; it would remains are found is sufficient to deter- be removed if the drainage were commine the relative age of extinct animals, plete. Let us look at the results which why should not the character of the soil naturally follow the planting and cultion which forest-trees are living, coupled vation of some kinds of forest-trees. In with the living history of these trees, be eight years the eucalyptus will attain a made to determine the order of succes- diameter of eighteen inches and a height sion in which they assumed possession of fifty feet. Experiments which I have of the virgin soil?

made determine these facts: A branch The bay-tree (Oreodaphne Californi- of this tree which contains 105 square ca) stands almost peerless in the Coast inches of leaf-surface will absorb 3.25 Range sylva. Its deep green cones of ounces of water in eighteen rs. The foliage, scattered through gulches and entire tree will furnish an area of 310,along hill-sides, give greater depth and 500 square inches of leaf-surface, and wildness to cañons, and mingle with the amount of water daily absorbed by the rounded tops of the evergreen oak the roots would equal 609 pounds, or to form the characteristic scenery of the seventy-six gallons. Given a stagnant rock-faced mountains. Early in Janua- swamp of 200 acres, each acre having ry its clusters of wax- like flowers ap- 200 trees, and the amount of water daily pear, half-hidden and protected from un- absorbed by the roots would be 3,040,timely cold by a profusion of thick shin- ooo gallons, or 405,333 cubic feet. This ing lanceolate leaves. The fruit of the would be equal to a constant stream runprevious season, about the size of a large ning at the rate of three miles per hour, filbert, holds its place beside the blos- of two feet wide and six inches deep. soms, so that every gradation of infio- This question has a practical import, rescence may be seen, from the half-de- as applied to two projects which are now veloped flower-bud to the mature carpel. being discussed, and to the results on Like the willow, its favorite locality is public health which would follow the


adoption of either: the irrigation of the Will extensive irrigation change the San Joaquin Valley, and the introduc- climatal condition of a district of countion of the water of Lake Tulare into try? The question has been practically San Francisco for economical purposes. answered in the mining districts of CalThe direct effect of irrigating the low ifornia and elsewhere. Before the forlands of the valley would be the forma- mation of ditches and the damming of tion of a larger area within which ma- the upper waters of rivers which form larial fevers would prevail; for it is well tributaries of the Sacramento and San known that there are lands along the Joaquin, the surface moisture of land San Joaquin and some of its tributaries, among the mountain foot-hills was gendry during the summer months, but erally evaporated by the middle of May which, on being plowed, liberate the or the first of June. At this time clouds subtle poison which engenders disease. ceased to form in the upper air, and by The great district in California which is day and night the unbroken clearness subject to malarial fevers includes large of the sky during the summer solstice portions of the Sacramento, the San permitted the full intensity of solar heat Joaquin, and the Tulare valleys, extend- to impinge on the denuded soil. The ing from the sixth standard north from heat thus acquired during the day was Mount Diablo base to the eighth stand- seldom radiated with sufficient rapidity ard south, covering an area of 375 miles in the night to bring the temperature of in length, with a width varying from two the air within range of the dew-point. to twenty-five miles. Much of this low In fact, during the latter part of summer land is known as tule swamp, from its the air was almost absolutely dry. The being covered with Scirpus lacustris absence of dew thus became a marked L., which grows in places from eight to feature of the interior climate. twelve feet high. Other portions have After the head - waters of the rivers a dense undergrowth of willow, which had been dammed, and ditches to the disappears in the neighborhood of the extent of 7,000 miles constructed, which tules, but which reasserts its claim to spread water during most of the sumthe watery soil in places along the whole mer through thousands of smaller chancourse of the valley.

nels, the air became so charged with This immense field of swamp and over- vapor that deposits of dew became the flowed land, covering an area of over rule instead of the exception. No oth6,000 square miles, has comparatively er change was manifest except a slight little population outside of Sacramento, reduction of temperature as a sequence Stockton, Marysville, and other cities, of evaporation. Beyond the results thus which are feeders to the agricultural foreshadowed in mining operations, and and mining population. Hence it is the certainty of securing fair crops, there difficult to estimate the area which may is nothing to be urged in favor of extenproperly be regarded as malarial. Phy- sive irrigation as compensatory to giving sicians are cognizant of many places greater activity and diffusion to malarialong the Merced and San Joaquin riv- al poisons. ers where the upturning of dry meadow The matter of cultivating forests besoil for agricultural purposes has been comes then a question of almost vital followed by malarial fever. During the importance to every settler within the construction of the Central Pacific Rail- precincts of this low land. It is not a road along the San Joaquin Valley, near- doubtful experiment as a hygienic measly every laborer became a victim to the ure. The medical faculty need not be same disease.

reminded of the conditions which in

crease the virulence of or destroy mala- A forest of the before - named magnirial poisons. Observation has estab- tude would contain 96,000,000 trees, and lished as facts: That excess of water in during every twenty-four hours there soil, by producing currents which carry would be exhaled 7,296,000,000 gallons, off the poison or dilute it to the extent or 980,000,000 cubic feet of water. This of rendering it innoxious, prevents the would be sufficient to fill a ditch fifty formation of miasma; and that a lack of feet wide, nine and five-tenths feet deep, water in soil, by abstracting a necessary and 375 miles long; which, flowing from factor to vegetable decomposition, also each extremity of the valley to its outprevents the development of disease. It let in San Pablo Bay at the rate of three is between these extremes that the for- miles per hour, would require two days ces operate which render active the tox- to empty itself. The water taken up ic properties of marsh miasm. There and exhaled by such a mass of trees must be added, however, a temperature would be equivalent to a constant stream ranging upward from 60° Fahrenheit, of this volume. and prolonged for weeks or months, This estimate represents the capabilbefore all the conditions which are nec- ity of daily absorption. The quantity essary to produce vegetable decomposi- of water which would actually be thus tion and miasma are fairly established. taken from the soil may fall far short of

What then is the modus operandi by this amount; for the ground, not being which forests purify the atmosphere and always saturated, would afford but a prevent the formation of marsh miasma? limited supply to the roots. The range It has been stated that 6,000 square in quantity between fact and theory will miles of the great valley are included not affect the argument, inasmuch as in overflowed lands, and this amount there is always maintained in living ormay be reclaimed.* Let us so enlarge ganizations a definite yet varying degree the experiment detailed on a previous of activity between the functions of the page as to make a belt of eucalyptus- system and its consumption of food. trees two miles wide, and extend it 375 But absorption of water and its submiles, or the entire length of the valley. sequent exhalation do not constitute the Nature works by small accretions, but process of nutrition and growth in the operates on a large scale. She would vegetable world. The water of the soil of herself execute all the work which is not merely holds in solution all the solid here laid out, were she allowed a little mineral matter which goes to make up time. But the aggressive spirit of Yan- the substance of the tree, but gaseous keeism must accomplish tremendous re- elements, either in a simple form as of sults within a few years of business life. atmospheric air, or combined as in carIt can not tolerate the idea of using up bonic acid, sulphureted hydrogen, and a few centuries out of the store house of other mephitic gases. Whatever there eternity, in order that a piece of swamp may be held in solution is, in a general land or a section of arid débris should sense, absorbed by the roots and conbe converted into a spot befitting fifty veyed with little or no change to the bushels of wheat to the acre. Fortu- leaves, which form the laboratory of the nately for science this spirit was not vegetable world. Carbon, hydrogen, "peeking” round in the palæozoic age, lime, potassa, soda, and other substanas all transitions between the awkward ces, are here subjected to changes, by Silurian and the post-tertiary era would the agency of solar light and heat, which have been totally ignored.

adapt them to the composition and the * Land Office Report, 1868.

structure of the tree. This chemical

activity is rapid in many growths, es- upward. At such times the incubation pecially in the eucalyptus. The strong of disease is active. aroma of its gum is diffused to a distance Unless the conditions be peculiar, a of thirty or forty feet. The hydrogen maximum temperature of 80° through which forms one of its elementary con- the day will be followed by a minimum stituents is derived from the decompo- temperature below 60° during the night. sition of water which the tree takes from Along sea-shore counties the thermal the soil. The entire process of vegeta- range is not so great, and in valleys ble life constantly carried on in effecting protected from ocean breezes the radithe assimilation of food not only returns ant heat during night arrests the cooling to the atmosphere oxygen, as a product process from inflowing air. of the decomposition of water and car- Let us see what disposition would be bonic acid, but restores the purity of all made of the vast amount of liquid daily other substances that are exhaled either absorbed and discharged into the atmosin a simple or compound form. Thus, phere. At 212° a cubic foot of water in whatever shape marsh miasma may will be converted into 1,696 cubic feet exist—whether held in solution by water of vapor. At 60°, with the barometer and diffused in the vapor of night, or at thirty inches, each cubic foot of air retained in the soil and liberated by the will contain 6.22 grains of vapor. The presence of water-it is certain to be 980,000,000 cubic feet of water will satdestroyed by an adequate development urate a belt of atmosphere 375 miles of forest growth. This is so fully rec- long, ten miles wide, and 1,200 feet in ognized in medical literature as to ren- thickness, which would be resting over der exemplifications unnecessary. the valley for the greater portion of ev

As another sequence of the activity ery twenty-four hours. But would the of vegetable growth, the cooling of the swamp-land yield this quantity of water atmosphere is prominent. This reduc- every day ? Estimating the average raintion of temperature is mainly due to ex- fall at eighteen inches, and excluding the halation of water from the leaves. This inflowing water from mountain streams, function is most active during the day; it would require over Soo days for the for the more rapid the evaporation, the forest to absorb all the moisture that the cooler does the air become: consequent- valley received during the winter months. ly, the greatest difference of temperature If this process commenced with the acbetween the open air and the shade of a tive growth of vegetation in February, tree is from noon until three o'clock P.M. and were to continue but 120 days, all This range, being affected by local caus- the requirements of growing crops would es, can not be precisely and uniformly be met without appropriating over oneindicated, except by actual experiment. sixth of the amount which fell upon the Where the thermometer stands in the land. Moreover, there would be a comshade at 85° Fahrenheit, it will be at pensating action constantly going on, in 100° in the sun-lit air, protected from di- consequence of the vapor rendered to rect solar rays; at the same time the the atmosphere being partially returned surface soil will indicate 115°. This is to the soil by condensation. the breathing temperature prevalent for The arid nature of parts of the San parts of several months along the great Joaquin Valley is not referable to high valley of which we have spoken. At temperature and evaporation alone. In times 130° or 140° are indicated by the the middle of the plains, east of Stockthermometer. It is very common for ton, excavation shows a succession of the night temperature to stand at 80° or strata formed of washed bowlders and coarse gravel, more than seventy feet in eter, which was almost filled with the depth, before a retentive water - bearing roots of a sycamore-tree that grew withbed is reached. Other parts of the val- in a rod of it. There is another well, in ley show a similar formation, and evi- the yard of the Congregational Church dence tends to the conclusion that the in Oakland, from ich was taken a inland sea which once covered this area solid mat of roots, none larger than a was obliterated by débris brought down thick knitting-needle; the whole about from the mountains on either side. In three feet in diameter and two feet in fact, the process of denudation is still thickness. These cases, among many, active, as may be seen along the entire are sufficient to show the extent of root course of the range. This deposit, be- development in the presence of a copiing coarse and loosely packed, can not ous supply of water. They also show retain the water which falls upon the the rapidity with which organic matter surface. Such is the character of more can be supplied to the soil from this than 2,000,000 acres of this arid land.

source; and, furthermore, the modus It is not possible to define the dis- operandi whereby a loose coarse depostance which the roots of trees will trav- it of purely mineral matter has its inel, under favorable circumstances, in terstitial spaces supplied with vegetable quest of water. Some years ago, in mold, and is thus converted into prothe process of grading Clay Street, San ductive soil. Francisco, excavation was made through These secondary results of foresta sand- bank to the depth of thirty feet. planting land, while being carried on A small scrub-oak, four inches in diam- far beneath the surface, are suppleeter, was growing on the crest of the mented by processes of trunk growth. hill, on the line of the cut. I traced its Everybody is familiar with the fact that main root thirty feet in a vertical line, under an old tree there is always from and at that depth it was still half an inch six to twelve inches of vegetable mold, in diameter. East of Alameda there is derived from the decomposition of leaves a hill-side cut, which gave origin some and bark which are annually shed. The years ago to a small land-slide, expos- weight of dried matter thus furnished, ing the root of an oak-tree. When I by a tree of the size indicated on a preobserved this for the first time, there was ceding page, will not fall short of 200 a small root - fibre, which looked like a pounds. A considerable portion of this piece of half-inch rope, stretched hori- is composed of organic matter, some of zontally for a distance of nearly forty which may be resolved by subsequent feet without any apparent diminution in oxidation. The balance constitutes the thickness. At the present time it is potassa, lime, silex, and other minerals, over three inches in diameter, and its which, held in solution by the water of distal extremity is doubtless over 100 the soil, has been taken up by the sap, feet from the trunk. Thus it is that the conveyed to the leaves, metamorphosed terminal roots of trees, through which into the solid material of the tree, and absorption takes place, will follow hori- partly returned to the earth through the zontally or downward the receding line leaves and bark. The results of this of moisture, to an extent that is deter- process, on a large scale and during mined by the texture of the soil. Roots, consecutive years, may be seen in any like branches, are always throwing out forest-growth which originated on a bed side - buds, which sometimes increase in of gravel. Fine mold fills the interstinumber to a marvelous extent. There ces between washed or angular pebbles, is a well in Alameda, four feet in diam- furnishing sustenance to a dense under

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