Moisture

“ Fig. 3.—Spores of Algæ and Molds in the Atmosphere.
the development of molds is dependent upon both heat and moisture. The effect of moisture, however, varies according to the season, and with changes in temperature. Dry weather diminishes the number of germs in summer, and increases it in winter, while moist weather operates in an inverse manner. ”

“ We now see that, as a living organism, it tends, on the one hand, to diminish the humidity of the air by sometimes absorbing moisture from it, and, on the other, to increase that humidity by pouring out into the atmosphere, in a vaporous form, the water it draws up through its roots. ”

“ Neither can the sun pull the moisture up through the tiny little tubes in the soil if we break those little tubes and crumble the tops into dust. No, you need not look for these tubes, Mary Frances; they are too tiny for you to see, but they act very much like blotting paper to bring the under moisture up to the surface, and unless they are broken and crumbled, the deep earth moisture goes sailing off into the air to meet the sun, as fast as if it ran out of a little spigot running it off, and the poor plant baby dries up for want of deep moisture near its roots. ”

“ In inhabited rooms the moisture increases as much as the organic matter, and the condition of the air is similar to that of the evenings of summer: whenever the temperature goes down a little, there is a deposit of dew; but, when the warmth increases, the air is laden with moisture, and the condition resembles that near a warm close vegetation. In both cases ventilation is wanted. Our walls become saturated with moisture if they are porous, if not porous they are covered with streams of water. ”

“ The quantity of moisture that the atmosphere keeps in circulation is, no doubt, just that quantity which is best suited to the well-being,'and most adapted to the proper development of the vegetable and animal kingdoms; and that quantity is dependent upon the arrangement and the proportions that we see in nature between the land and the water—between mountain and desert, river and sea. ”

“ The moisture is used up and the fruit makes the heat rise, and so the fruit will be bitter, and the stones in the fruit will be pyramidal in form on account of the upward attraction of the heat and the downward attraction of the cold and moisture which are of the same nature as sour water; and the moisture remains in the trunk of the tree, which consequently thickens, while its extremities are thin. ”

“ When the air—or rather, the water vapor itself—is near the point of saturation it is moist to the senses. Hygroscopic substances, such as sugar, salt and many other substances, absorb moisture; sized paper and starched fabrics swell and become limp. ”

“ But after any number of days and nights of rain, and in all places exposed to returning sunshine and breezes, the distribution of the moisture tells. So soon as the rain has ceased, all water that can run off is of course gone from the steep hill-sides; there remains only the thin adherent film of moisture to be dried; but that film is spread over a complex texture—all manner of crannies, and bosses, and projections, and filaments of moss and lichen, exposing a vast extent of drying surface to the air. ”

“ Roots seek at once heat and moisture; if the moisture awaits them close to the surface, of course they mainly run there, because the heat is there greatest. If moisture fails there, they must descend to seek it, even at the cost of finding the heat inadequate—though heat increases and descends under the fervid suns which rob the surface of moisture. ”

“ The necessary temperature is speedily attained by the heating action of the sun's rays, when the soil is dry; but when it is wet, the heat is expended in evaporating the moisture with which it is saturated ”

“ The object being to expel the moisture in the most gentle manner, and, at the same time, to allow the leaves to remain as soft and pliable as possible. When the sun is clear and powerful the moisture evaporates too rapidly, and the leaves are left crisp, coarse, and not in a proper state to undergo the remaining part of the process. ”

“ Fig. 5.—Apparatus to illustrate the Mode in which the Influence of Gravity is overcome by the Effect of Greater Moisture on one Side of the Root. (Sachs.) With a view to seeing whether this sensitiveness to moisture was localized like the sensitiveness to gravity, Darwin covered the tips of a number of seedlings with grease, and then subjected them to an excess of moisture on one side. ”

“ The qualities hitherto sought in a hygrometer, or instrument to discover the degrees of moisture and dryness [136] in the air, seem to have been, an aptitude to receive humidity readily from a moist air, and to part with it is as readily to a dry air. ”

“ Now the parts of plants are usually rare, because the heat draws the moisture into the extremities of the plant, and the material is distributed through all its parts, and that which is superfluous will flow away; just as in a bath the heat attracts the moisture and turns it into vapour which rises, and, when it is present in superfluity, it will turn into drops of water. ”

“ These observations and experiments establish the fact that the drops which first make their appearance on grass on dewy nights are not dew-drops at all, but the exuded watery juices of the plants.
If now we look at dead leaves we shall find a difference of formation of the moisture on a dewy night: the moisture is spread equally over, where equally exposed. The moisture exuded by the healthy grass is always found at a point situated near the tip of the blade, forming a drop of some size ”

“ From this: dry air, when coming in contact with wet objects, absorbs the moisture, and by this dries the object somewhat. If there be no wind, the moistened air will remain around the wet object, and the drying goes on very slowly. But so soon as a little wind arises, the moist air is moved away, new dry air constantly takes its place, and coming into contact with the wet article, effects in a very short time the desired result. ”

“ Not all scientific works, however, make this incautious application of the fact that dew results from the condensation of moisture of the air in contact with cooler bodies. Farmers have quite universally accepted the view quoted, and believe that soils gain moisture by night from the air. ”

“ When air holds all the moisture it can sustain, its moisture is said to be at 100 per cent.; when it holds only one-half as much as its temperature demands, it is said to be at 50 per cent.; and when it holds three-fourths of what its temperature requires, it is at 75 per cent. ”

“ Determination of Moisture.—Heat two to five grams of the air-dried soil in a flat-bottomed, tared platinum dish; heat for five hours in a water-oven kept briskly boiling; cover the dish, cool in a desiccator, and weigh.
Repeat the heating, cooling, and weighing at intervals of two hours till constant weight is found, and estimate the moisture by the loss of weight. Weigh rapidly to avoid absorption of moisture from the air. ”

“ Water, a solid substance, heat, a beginning putrefaction, appear indispensable to the production and propagation of the animalcules; and such conditions are in fact always united. Without moisture, they never live; a solid substance must offer a basis to moisture, and, according to physical laws, the contact of the one with the other generates heat, and only by the simultaneous action of moisture and heat can putrefaction take place. ”

“ The moisture which floats in the atmosphere is of most essential use to vegetable life. [7] “The leaves of living plants appear to act upon this vapour in its elastic form, and to absorb it. Some vegetables increase in weight from this cause when suspended in the atmosphere and unconnected with the soil, as the house-leek and the aloe. In very intense heats, and when the soil is dry, the life of plants seems to be preserved by the absorbent power of their leaves.” ”

“ If it be subjected to the influence of an atmosphere containing a greater amount of moisture it increases in bulk, or, as it is popularly termed, it swells; in a drier atmosphere it shrinks and is apt to crack. ”

“ The third element concerned in the climate, namely, moisture, has now to be considered, and it is important from the fact that in a moister climate the percentages both of glucose and of acids in the grape are diminished. It is also important for another reason, namely, that while heat and light are unalterable, moisture may be produced by irrigation. ”

“ The great condensation of moisture on the summits of hills has another cause, which is the dashing of moving clouds against them, in misty days this is often seen to have great effect on plains, where an eminent tree by obstructing the mist as it moves along shall have a much greater quantity of moisture drop from its leaves than falls at the same time on the ground in its vicinity. ”

“ We must separate dew from rain, and the moisture of fogs, and limit the application of the term to what is really meant, which is the spontaneous appearance of moisture on substances exposed in the open air when no rain or visible wet is falling. ”

“ The moisture sensation of the air is its humidity. Before saturation is reached, the moisture is in the form of vapor; at the point of saturation it may appear in the air as fog, or cloud; when the ground temperature reaches the point of saturation condensation takes place in the form of dew ”

“ The rapidity of the chemical change is chiefly governed by the proportion of moisture, being greatly accelerated by wetting the bruised kernels or leaves, and stopped altogether by drying, while the moisture of the living plant permits only a gradual rate of the transformation. ”

“ A moist genial atmosphere too is essential, a point requiring unremitting attention on account of the necessity of keeping up strong fires. With moisture as with heat, the cultivator must hold his hand somewhat in very severe or very dull weather; but while heat must not drop so as to chill the progressing vegetation, so neither must the lack of moisture parch the plants so as to check their growth. ”

“ No water, no plant. Then, too, the earth cooled more and more, and from being uniformly warm and moist, which was just the best conditions for plants to live without taking any trouble about it, the air was sometimes colder and contained less moisture. ”

“ As the cold tumbler condenses the moisture in the air, so does the earth at night, it being cooled by radiation, condense the moisture which has accumulated in the air by evaporation during the heat of the day. ”

“ The water held in a state of solution by the atmosphere, in consequence of the heat which it acquires from the perpendicular rays of the sun, is so much greater in quantity than what it can retain in situations not exposed to an equal degree of heat, that every thing that is not exposed to the direct rays of the sun, becomes covered with a great degree of moisture ”

“ Part of the moisture which vegetable earth or soil derives from the atmosphere passes into the subjacent mass of rock, but this may again be compensated by evaporation; on which account the soil of such rocks as have but a small attraction for water usually dries up more readily than soils whose solid substratum attracts and retains the moisture in a greater degree. ”

“ Fig. 38. A cross section through one of the foot-prints.
The prudent farmer will take measures to prevent the escape of this moisture into the air. All the film-moisture (on the soil particles) needs to be carefully conserved or saved, for the plants will need very large amounts of moisture before they mature, and they can draw their supply only from this film-moisture. [121] We can again apply the lesson learned in the woods. The soil there is always moist; the leaves form a cover, or blanket, which prevents the evaporation of moisture. ”

“ Evaporometer.—The moisture in the atmosphere comes from the surface of the earth or ocean by evaporation, a process which goes on continually, replacing the moisture that is precipitated as rain, hail, snow and dew, and maintaining the total quantity of the moisture in the atmosphere at a very uniform figure. ”

“ The moisture in the ascending air is condensed by cooling both as it ascends and as it expands into the low-pressure core. The cloud-funnel appears to grow downwards because the moisture in the air is condensed more rapidly than the air itself, following a spiral course, ascends. ”

“ Trees absorb or suck up moisture from the earth; and the particles which compose them are so combined and adjusted as to facilitate this operation. Plant a post deeply and firmly in the ground, butt-end downward, and it will continue to absorb moisture from the earth as it did when alive ”

“ If the temperature of the confined space be increased, opportunity will thereby be provided for the vaporization of more water, but if it be decreased, its capacity for moisture will be reduced and visible water will be deposited. ”

“ Again, the air should be pure, and free from redundant moisture. In the warm mornings of July and August, the air is loaded with moisture and impurities, and the perspirable matter is not removed from the system as it is when the air is pure and dry. ”

“ It follows that when exposed to moisture, as its texture is not loose and porous, it cannot take in liquid on account of its compactness, but, withdrawing from the moisture, it resists it and warps, thus making cracks in the structures in which it is used.
9. The winter oak, being composed of a moderate amount of all the elements, is very useful in buildings, but when in a moist place, it takes in water to its centre through its pores, its air and fire being expelled by the influence of the moisture, and so it rots. ”

“ The evaporation of the juices of trees and other plants is doubtless their most important thermoscopic function, and as recent observations lead to the conclusion that the quantity of moisture exhaled by vegetables has been hitherto underrated, we must ascribe to this element a higher value than has been usually assigned to it as a meteorological influence. ”