Chapter 37

EFFECTS OF DRAINAGE UPON THE CONDITION OF THE SOIL.

Drainage deepens the Soil, and gives the roots a larger pasture.--Cobbett's Lucerne 30 feet deep.--Mechi's Parsnips 13 feet long!--Drainage promotes Pulverization.--Prevents Surface-Washing.--Lengthens the Season.--Prevents Freezing out.--Dispenses with Open Ditches.--Saves 25 per cent. of Labor.--Promotes absorption of Fertilizing Substances from the Air.--Supplies Air to the Roots.--Drains run before Rain; so do some Springs.--Drainage warms the Soil.--Corn sprouts at 55°; Rye on Ice.--Cold from Evaporation.--Heat will not pass downward in Water.--Count Rumford's Experiments with Hot Water on Ice.--Aeration of Soil by Drains.

The benefits which high-lands, as we ordinarily call them, in distinction from swamp or flowed lands, derive from drainage, may be arranged in two classes, _mechanical_ and _chemical_; though it is not easy, nor, indeed, is it important, to maintain this distinction in all points. Among those which partake rather of the nature of mechanical changes, are the following:

_Drainage deepens the soil._ Every one who has attempted to raise deep-rooted vegetables upon half-drained swamp-land, has observed the utter impossibility of inducing them to extend downward their usual length. Parsnips and carrots, on such land, frequently grow large at the top, but divide into numerous small fibres just below the surface, and spread in all directions. No root, except those of aquatic plants, will grow in stagnant water. If, therefore, it is of any advantage to have a deep, rather than a shallow soil, it is manifestly necessary, from this consideration alone, to lower the line of standing water, at least, to the extent to which the roots of our cultivated crops descend. A deep soil is better than a shallow one, because it furnishes a more extensive feeding-ground for the roots. The elements of nutrition, which the plant finds in the soil, are not all upon the surface. Many of them are washed down by the rains into the subsoil, and some are found in the decomposing rocks themselves. These, the plants, by a sort of instinct, search out and find, as well in the depths of the earth as at its surface, if no obstacle opposes. By striking deep roots again, the plants stand more firmly in the earth, so that they are not so readily drawn out, or shaken by the winds. Indeed, every one knows that a soil two feet deep is better than one a foot deep; and market-gardeners and nursery-men show, by their practice, that they know, if others do not, that a trenched soil three feet deep is better than one of any less depth. We all know that Indian corn, in a dry soil, sends down its rootlets two feet or more, as well as most of the grasses. Cobbett says: "The lucerne will send its roots thirty feet into a dry bottom!" The Chinese yam, recently introduced, grows downward two or three feet. The digging of an acre of such a crop, by the way, on New England soil generally, would require a corps of sappers and miners, especially when we consider that the yam grows largest end downward. However, the yam may prove a valuable acquisition to the country. Every inch of additional soil gives 100 tons of active soil per acre.

Says Mr. Denton:

"I have evidence now before me, that the roots of the wheat plant, the mangold wurzel, the cabbage, and the white turnip, frequently descend into the soil to the depth of three feet. I have myself traced the roots of wheat nine feet deep. I have discovered the roots of perennial grasses in drains four feet deep; and I may refer to Mr. Mercer, of Newton, in Lancashire, who has traced the roots of rye grass running for many feet along a small pipe-drain, after descending four feet through the soil. Mr. Hetley, of Orton, assures me that he discovered the roots of the mangolds, in a recently made drain, five feet deep; and the late Sir John Conroy had many newly-made drains, four feet deep, stopped by the roots of the same plants."

Mr. Sheriff Mechi's parsnips, however, distance anything in the way of deep rooting that has yet been recorded. The Sheriff is a very deep drainer, and an enthusiast in agriculture, and Nature seems to delight to humor his tastes, by performing a great many experiments at his famous place called Tiptree Hall. He stated, at a public meeting, that, in his neighborhood, where a crop of parsnips was growing on the edge of a clay pit, the roots were observed to descend 13 feet 6 inches; in fact, the whole depth to which this pit had once been filled up!

_Drainage assists pulverization._ It was Tull's theory that, by the comminution, or minute division, of soils alone, without the application of any manures, their fertility might be permanently maintained; and he so far supported this theory as, by repeated plowings, to produce twelve successive crops of wheat on the same land, without manure. The theory has received support from the known fact, that most soils are benefitted by Summer fallowing. The experiments instituted for the purpose of establishing this theory, although they disproved it, showed the great value of thorough pulverization. It is manifest that a wet soil can never be pulverized. Plowing clayey, or even loamy soil, when wet, tends rather to press it together, and render it less pervious to air and water.

The first effect of under-draining is to dry the surface-soil, to draw out all the water that will run out of it, so that, in early Spring, or in Autumn, it may be worked with the plow as advantageously as undrained lands in mid-Summer.

Striking illustrations of the benefits of thorough pulverization will be found in the excellent remarks of Dr. Madden, given in a subsequent chapter.

_Drainage prevents surface-washing._ All land which is not level, and is not in grass, is liable to great loss by heavy rains in Spring and Autumn. If the land is already filled with water, or has not sufficient drainage, the rain cannot pass directly downward, but runs away upon the surface, carrying with it much of the soil, and washing out of what remains, of the valuable elements of fertility which have been applied with such expense. If the land be properly drained, the water falling from the clouds is at once absorbed, and passes downwards, saturating the soil in its descent, and carrying the soluble substances with it to the roots, and the surplus water runs away in the artificial channels provided by the draining process. So great is the absorbent power of drained land, that, after a protracted drought, all the water of a heavy rainstorm will be drunk up and held by the soil, so that, for a day or two, none will find its way to the drains, nor will it run upon the surface.

_Drainage lengthens the season for labor and vegetation._ In the colder latitudes of our country, where a long Winter is succeeded by a torrid Summer, with very little ceremony by way of an intervening Spring, farmers have need of all their energy to get their seed seasonably into the ground. Snow often covers the fields in New England into April; and the ground is so saturated with water, that the land designed for corn and potatoes, frequently cannot be plowed till late in May. The manure is to be hauled from the cellar or yard, over land lifted and softened by frost, and all the processes of preparing and planting, are necessarily hurried and imperfect. In the Annual Report of the Secretary of the Board of Agriculture, of the State of Maine, for 1856, a good illustration of this idea is given: "Mr. B. F. Nourse, of Orrington, plowed and planted with corn a piece of his drained and subsoiled land, in a drizzling rain, after a storm of two days. The corn came up and grew well; yet this was a clayey loam, formerly as wet as the adjoining grass-field, upon which oxen and carts could not pass, on the day of this planting, without cutting through the turf and miring deeply. The nearest neighbor said, if he had planted that day, it must have been from a raft." Probably two weeks would be gained in New England, in Spring, in which to prepare for planting, by thorough-drainage, a gain, which no one can appreciate but a New England man, who has been obliged often to plow his land when too wet, to cut it up and overwork his team, in hauling on his manure over soft ground, and finally to plant as late as the 6th of June, or leave his manure to waste, and lose the use of his field till another season; and all because of a surplus of cold water.

Mr. Yeomans, of New York, in a published statement of his experience in draining, says, that on his drained lands, "the ground becomes almost as dry in two or three days after the frost comes out in Spring, or after a heavy rain, as it would do in as many weeks, before draining." But the gain of time for labor is not all. We gain time also for vegetation, by thorough-drainage. Ten days, frequently, in New England, may be the security of our corn-crop against frost. In less than that time, a whole field passes from the milky stage, when a slight frost would ruin it, to the glazed stage, when it is safe from cold; and twice ten days of warm season are added by this removal of surplus water.

_Drainage prevents freezing out._ Mr. John Johnston, of Seneca County, New York, in 1851, had already made sixteen miles of tile drains. He had been experimenting with tiles from 1835, and had, on four acres of his drained clayey land, raised the largest crop of Indian corn ever produced in that county--eighty-three bushels of shelled corn to the acre.

He states, that on this clayey soil, when laid down to grass, "not one square foot of the clover froze out." Again he says, "Heretofore, many acres of wheat were lost on the upland by freezing out, and none would grow on the lowlands. Now there is no loss from that cause."

The growing of Winter wheat has been entirely abandoned in some localities on account of freezing out, or Winter-killing; and one of the worst obstacles in the way of getting our lands into grass, and keeping them so, is this very difficulty of freezing out. The operation seems to be merely this: The soil is pulverized only to the depth of the plow, some six or eight inches. Below this is a stratum of clay, nearly impervious to water. The Autumn rains saturate the surface soil, which absorbs water like a sponge. The ground is suddenly frozen; the water contained in it crystallizes into ice; and the soil is thrown up into spicules, or honey-combs; and the poor clover roots, or wheat plants, are drawn from their beds, and, by a few repetitions of the process, left dead on the field in Spring. Draining, followed by subsoiling, lets down the falling water at once through the soil, leaving the root bed of the plants so free from moisture, that the earth is not "heaved," as the term is, and the plants retain their natural position, and awaken refreshed in the Spring by their Winter's repose.

_There are no open ditches on under-drained land._ An open ditch in a tillage or mowing-field, is an abomination. It compels us, in plowing, to stop, perhaps midway in our field; to make short lands; to leave headlands inconvenient to cultivate; and so to waste our time and strength in turning the team, and treading up the ground, instead of profitably employing it in drawing a long and handsome furrow the whole length of the field, as we might do were there no ditch. Open ditches, as usually made, obstruct the movement of our teams as much as fences, and a farm cut into squares by ditches, is nearly as objectionable as a farm fenced off into half or quarter-acre fields.

In haying, we have the same inconvenience. We must turn the mowing-machine and horse-rake at the ditch, and finish by hand-labor, the work on its banks; we must construct bridges at frequent intervals, and then go out of our way to cross them with loads, cutting up the smooth fields with wheels and the feet of animals. Or, what is a familiar scene, when a shower is coming up, and the load is ready, Patrick concludes to drive straight to the barn, across the ditch, and gets his team mired, upsets his load, and perhaps breaks the leg of an animal, besides swearing more than half a mile of hard ditching will expiate. Such accidents are a great temptation to profanity, and under-draining might properly be reckoned a moral agent, to counteract such traps and pitfalls of the great adversary.

A moment's thought will satisfy any farmer who has the means, that true economy dictates a liberal expenditure of labor, at once, to obviate these difficulties, rather than be subject for a lifetime to the constant petty annoyances which have been named.

Open ditches, even when formed so skillfully that they may be conveniently crossed, or water-furrows which remain where land is laid into ridges by back-furrowing, as much of our flat land must be, if not under-drained, are serious obstructions, at the best.

They render the soil unequal in depth, taking it from one point where it is wanted, and heaping it upon another where it is not wanted, thus giving the crops an uneven growth. They render the soil also unequal in respect to moisture, because the back or top of the ridge must always be drier than the furrow.

Thorough-drained land may be laid perfectly flat, giving us, thus, the control of the whole field, to divide and cultivate according to convenience, and making it of uniform texture and temperature.

Attempts have been made, to estimate the saving in the number of horses and men by drainage, and it is thought to be a reasonable calculation to fix it at one in four, or twenty-five per cent. It probably will strike any farmer as a fair estimate, that, on land which needs drainage, it will require four horses and four men to perform the same amount of cultivation, that three men and three horses may perform on the same land well drained.

_Drained land will not require re-planting._ There is hardly a farmer in New England, who does not, each Spring, find himself compelled to re-plant some portion of his crop. He is obliged to hurry his seed into the ground, at the earliest day, because our season for planting is short at the best. If, after this, a long cold storm comes, on wet land, the seed rots in the ground, and he must plant again, often too late, incurring thus the loss of the seed, the labor of twice doing the same work, the interruption of his regular plan of business, and often the partial failure of his crop.

Upon thorough-drained land, this cost and labor could rarely be experienced, because nothing short of a small deluge could saturate well drained land, so as to cause the seed to fail, if sowed or planted with ordinary care and prudence, as to the season.

_Drained land is lighter to work._ It is often difficult to find a day in the year, when a wet piece of land is in suitable condition to plow. Usually, such tracts are unequal, some parts being much wetter than others, because the water settles into the low places. In such fields, we now drive our team knee deep into soft mud, and find a stream of water following us in the furrow, and now we rise upon a knoll, baked hard, and sun-cracked; and one half the surface when finished is shining with the plastered mud, ready to dry into the consistency of bricks, while the other is already in hard dry lumps, like paving stones, and about as easily pulverized.

This is hard work for the team and men, hard in the plowing, and hard through the whole rotation. The same field, well drained, is friable and porous, and uniform in texture. It may be well plowed and readily pulverized, if taken in hand at any reasonable season.

Land which has been puddled by the tread of cattle, or by wheels, acquires a peculiar consistency, and a singular capacity to hold water. Certain clays are wet and beaten up into this consistency, to form the bottoms of ponds, and to tighten dams and reservoirs. A soil thus puddled, requires careful treatment to again render it permeable to water, and fit for cultivation. This puddling process is constantly going on, under the feet of cattle, under the plow and the cart-wheels, wherever land containing clay is worked upon in a wet state. Thus, by performing a day's work on wet land, we often render necessary as much additional labor as we perform, to cure the evil we have done.

_We may haul loads without injury on drained land._ On many farms, it is difficult to select a season for hauling out manure, or carting stones from place to place, when great injury is not done to some part of the land by the operation. Many farmers haul out their manure in Winter, to avoid cutting up their farms; admitting that the manure is wasted somewhat by the exposure, but, on the whole, choosing this loss as the lesser evil. In spreading manure in Spring, we are often obliged to carry half loads, because the land is soft, not only to spare our beasts, but also to spare our land the injury by treading it. Drained land is comparatively solid, especially in Spring, and will bear up heavy loads with little injury.

_Drained land is least injured by cattle in feeding._ Whether it is good husbandry to feed our mowing fields at any time, is a question upon which farmers have a right to differ. Without discussing the question, it is enough for our purpose, that most farmers feed their fields late in the Autumn. Whether we approve it, or not, when the pastures are bare and burnt up, and the second crop in the home-field is so rich and tempting, and the women are complaining that the cows give no milk, we usually bow to the necessity of the time, and "turn in" the cows. The great injury of "Fall-feeding" is not usually so much the loss of the grass-covering from the field, as the poaching of the soil and destruction of the roots by treading. A hard upland field is much less injured by feeding, than a low meadow, and the latter less in a dry than a wet season. By drainage, the surplus water is taken from the field. None can stand upon its surface for a day after the rain ceases. The soil is compact, and the hoofs of cattle make little impression upon it, and the second or third crop may be fed off, with comparatively little damage.

_Weeds are easily destroyed on drained land._ If a weed be dug or pulled up from land that is wet and sticky, it is likely to strike root and grow again, because earth adheres to its roots; whereas, a stroke of the hoe entirely separates the weeds in friable soil from the earth, and they die at once. Every farmer knows the different effect of hoeing, or of cultivating with the horse-hoe or harrow, in a rain storm and in dry weather. In one case, the weeds are rather refreshed by the stirring, and, in the other, they are destroyed. The difference between the surface of drained land and water-soaked land is much the same as that between land in dry weather under good cultivation, and land just saturated by rain.

Again, there are many noxious weeds, such as wild grasses, which thrive only on wet land, and which are difficult to exterminate, and which give us no trouble after the land is lightened and sweetened by drainage. Among the effects of drainage, mainly of a chemical nature, on the soil, are the following:

_Drainage promotes absorption of fertilizing substances from the air._ The atmosphere bears upon its bosom, not only the oxygen essential to the vitality of plants, not only water in the form of vapor, to quench their thirst in Summer droughts, but also various substances, which rise in exhalations from the sea, from decomposing animals and vegetables, from the breathing of all living creatures, from combustion, and a thousand other causes. These would be sufficient to corrupt the very air, and render it unfit for respiration, did not Nature, with her wondrous laws of compensation, provide for its purification. It has already been stated, how the atmosphere returns to the hills, in clouds and vapor, condensed at last to rain, all the water which the rivers carry to the sea; and how the well-drained soil derives moisture, in severest time of need, from its contact with the vapor-loaded air. But the rain and dew return not their waters to the earth without treasures of fertility. Ammonia, which is one of the most valuable substances found in farm-yard manures, and which is a constant result of decomposition, is absorbed in almost incredible quantities by water. About 780 times its own bulk of ammonia is readily absorbed by water at the common temperature and pressure of the atmosphere; and, freighted thus with treasures for the fields, the moisture of the atmosphere descends upon the earth. The rain cleanses the air of its impurities, and conveys them to the plants. The vapors of the marshes, and of the exposed manure heaps of the thriftless farmer, are gently wafted to the well-drained fields of his neighbor, and there, amidst the roots of the well-tilled crops, deposit, at the same time, their moisture and fertilizing wealth.

Of the wonderful power of the soil to absorb moisture, both from the heavens above and the earth beneath--by the deposition of dew, as well as by attraction--we shall treat more fully in another chapter. It will be found to be intimately connected with the present topic.

_Thorough drainage supplies air to the roots._ Plants, if they do not breathe like animals, require for their life almost the same constant supply of air. "All plants," says Liebig, "die in soils and water destitute of oxygen; absence of air acts exactly in the same manner as an excess of carbonic acid. Stagnant water on a marshy soil excludes air, but a renewal of water has the same effect as a renewal of air, because water contains it in solution. When the water is withdrawn from a marsh, free access is given to the air, and the marsh is changed into a fruitful meadow." Animal and vegetable matter do not decay, or decompose, so as to furnish food for plants, unless freely supplied with oxygen, which they must obtain from air. A slight quantity of air, however, is sufficient for putrefaction, which is a powerful deoxydizing process that extracts oxygen even from the roots of plants.

We are accustomed to think of the earth as a compact body of matter, vast and inert; subject, indeed, to be upheaved and rent by volcanoes and earthquakes, but as quite insensible to slight influences which operate upon living beings and upon vegetation. This, however, is a great mistake; and it may be interesting to refer to one or two facts, which illustrate the wonderful effect of changes of the atmosphere upon the soil, and upon the subterranean currents of the earth. The following is from remarks by Mr. Denton, in a public address:

"But, as a proof of the sensibility of a soil drained four feet deep, to atmospheric changes, I may mention, that my attention has been, on more than one occasion, called to the circumstance that drains have been observed to run, after a discontinuance of that duty, without any fall of rain on the surface of the drained land; and, upon reference to the barometer, it has been found that the quicksilver has fallen whenever this has occurred. Mr. George Beaumont, jun., who first afforded tangible evidence of this extraordinary circumstance, has permitted me to read the following extracts of his letter:

"'I can verify the case of the drains running without rain, during a falling barometer, beyond all doubt.

"'The case I named to you last year of the barometer falling four days consecutively, and with rapidity, was a peculiarly favorable time for noticing it, as it occurred in a dry time, and the drains could be seen distinctly. My man, on being questioned and cautioned by me not to exaggerate, has declared the actual stream of water issuing from one particular drain to be as thick as a three-eighth-inch wire. All the drains ran--they did more than drop--and ditches, which were previously dry, became quite wet, with a perceptible stream of water; this gradually ceased with the change in the density of the atmosphere, as shown by the barometer.

"'During last harvest, 1855, the men were cutting wheat, and on getting near to a drain outlet, the ditch from the outlet downwards was observed to be wet, and the drain was dripping. No rain fell in sufficient quantity to enter the ground. The men drank of the water while they were cutting the wheat. A few days after, it was dry again. I have seen and noticed this phenomenon myself.'

"A correspondent of the _Agricultural Gazette_ has stated, that Professor Brocklesby, of Hartford, in America, had observed the same phenomena, in the case of two springs in that country; and explained, that the cause was 'the diminished atmospheric pressure which exists before a rain.'"

Dr. Lardner states many facts which support the ideas above suggested. In his lectures on science, he says: "When storms are breaking in the heavens, and sometimes long before their commencement, and when their approach has not yet been manifested by any appearances in the firmament, phenomena are observed, apparently sympathetic, proceeding from the deep recesses of the earth, and exhibited under very various forms at its surface." Dr. Lardner cites many instances of fountains which, when a storm is approaching, burst forth with a violent flow of water, before any rain has fallen.

The cases named by Prof. Brocklesby, referred to by Mr. Denton, are those of a spring in Rutland, Vermont, and a brook in Concord, Massachusetts. Prof. Brocklesby states, as the result of his personal observation, that the spring referred to, supplies an aqueduct; that, in several instances, when the spring had become so low, in a time of drought, that no water ran in the aqueduct, it suddenly rose so as to fill the pipes, and furnish a supply of water, before any rain had fallen in the neighborhood. This occurrence, he says, was familiar to the occupants of the premises, and they expected rain in a few days after this mysterious flow of water; which expectations were usually, if not always, realized.

The other instance is that of a brook in Concord, Mass., called Dodge's brook, which Prof. B. says, he was informed, commenced frequently to rise very perceptibly before a drop of rain had fallen.

We have inquired of our friends in Concord about this matter, and find that this opinion is entertained by many of the people who live near this brook, and it is probably well founded, though we cannot ascertain that accurate observations have been made, so as to afford any definite results.

_Thorough drainage warms the soil._ It has been stated, on high authority, that drainage raises the temperature of the soil, often as much as 15° F. Indian corn vegetates at about 55°. At 45°, the seed would rot in the ground, without vegetating. The writer, however, has seen rye sprouted upon ice in an ice-house, with roots two inches long, so grown to the ice that they could only be separated by thawing. Winter rye, no doubt, makes considerable growth under snow. Cultivated plants, in general, however, do not grow at all, unless the soil be raised above 45°. The sun has great power to warm dry soils, and, it is said, will often raise their temperature to 90° or 100°, when the air in the shade is only 60° or 70°. But the sun has no such power to warm a wet soil, and for several reasons, which are as follows:

1. _The soil is rendered cold by evaporation._ If water cannot pass through the land by drainage, either natural or artificial, it must escape, if at all, at the surface, by evaporation. Now, it is a fact well known, that the heat disappears, or becomes latent, by the conversion of water into vapor. Every child knows this, practically, at least, who, in Winter, has washed his hands and gone out without drying them. The same evaporation which thus affects the hands, renders the land cold, when filled with water, every gallon of which thus carried off requires, and actually carries off, as much heat as would raise five and a half gallons of water from the freezing to the boiling point.

Morton, in his "Encyclopædia of Agriculture," estimates that it would require an expenditure of nearly 1,200 pounds of coal per day, to evaporate artificially one half the rain which falls on an acre during the year. In other words, about 219 tons of coals annually, would be required for every acre of undrained land, so as to allow the free use of the sun's rays for the legitimate purpose of growing and maturing the crops cultivated upon it. It will not then be surprising that undrained soils are, in the language of the farmer, "cold."

2. _Heat will not pass downward in water._ If, therefore, your soil be saturated with water, the heat of the sun, in Spring, cannot warm it, and your plowing and planting must be late, and your crop a failure. Count Rumford tried many experiments to illustrate the mode of the propagation of heat in fluids, and his conclusion, it is presumed, is now held to be the true theory, that heat is transmitted in water only by the motion of the particles of water; so that, if you could stop the heated particles from rising, water could not be warmed except where it touches the vessel containing it. Heat applied to the bottom of a vessel of water warms the particles in contact with the vessel, and colder particles descend, and so the whole is warmed.

Heat, applied to the surface of the water, can never warm it, except so far as it is conducted downward by some other medium than the water itself. Count Rumford confined cakes of ice in the bottom of glass jars, and, covering it with one thickness of paper, poured boiling-hot water on the top of it, and there it remained for hours without melting the ice. The paper was placed over the ice, so that the hot water could not be poured on it, which would have thawed it at once. Every man who has poured hot water into a frozen pump, hoping to thaw out the ice by this means, has arrived at the fact, if not at the theory, that ice will not melt by hot water on the top of it. If, however, a piece of lead pipe be placed in the pump, resting on the ice, and hot water be poured through it, the ice will melt at once. In the first instance, the hot water in contact with the ice becomes cold; and there it remains, because cold water is heavier than warm, and there it will remain, though the top be boiling. But when hot water is poured through the pipe, the downward current drives away the cold water, and brings heated particles in succession to the ice.

Heat is propagated in water, then, only by circulation; that is, by the upward movement of the heated particles, and the downward movement of the colder ones to take their place. Anything which obstructs circulation, prevents the passage of heat. Chocolate retains heat longer than tea, because it is thicker, and the hot particles cannot so readily rise to be cooled at the surface. Count Rumford illustrated this fact satisfactorily, by putting eider-down into water, which was found to obstruct the circulation, and to prevent the rapid heating and cooling of it. The same is true of all viscous substances, as starch and glue; and so of oil. They retain heat much longer than water or spirits.

In a soil saturated with water, or even in water thickened with mud, there could then be but little circulation of the particles, even were the heat applied at the bottom instead of the top. Probably the soil, though saturated with water, does, to some extent, transmit heat from one particle of earth to another, but it must be but very slowly.

In the chapter upon Temperature as affected by Drainage, farther illustrations of this point may be found.

AERATION BY DRAINS.

Among the advantages of thorough-drainage, is reckoned by all, the circulation of air through the soil. No drop of water can run from the soil into a drain without its place being supplied by air, unless there is more water to supply it; so that drainage, in this way, manifestly promotes the permeation of air through the soil.

But it is claimed that drains may be made to promote circulation of air in another way, and in dry times, when no water is flowing through them, by connecting them together by means of a header at the upper ends, and leaving an opening so that the air may pass freely through the whole system. Our friend, Prof. Mapes, is an advocate for this practice, and certainly the theory seems well supported. It is said that in dry, hot weather, when the air is most highly charged with moisture, currents thus passing constantly through the earth, must, by contact with the cooler subsoil, part with large quantities of moisture, and tend to moisten the soil from the drains to the surface, giving off also with the moisture whatever of fertilizing elements the air may bear with it.

This point has not escaped the notice of English drainers. Mr. J. H. Charnock, an assistant commissioner under the Drainage act, in 1843, read a paper in favor of this practice, but in 1849 he published a second article in which he suggests doubts of the advantages of such arrangements, and says he has discontinued their application. He says they add to the cost of the work, and tend to the decay of the pipes, and to promote the growth into the pipes, of any roots that may approach them.

Mr. Parkes, in a published article in 1846, speaks of this idea, but passes it by as of very little importance. Mr. Denton quotes the authority of some of his correspondents strongly in favor of this theory. After trying some experiments himself upon clay soil, he admits the advantages of such an arrangement for such soil, in the following not very enthusiastic terms:

"It will be readily understood that as clay will always contract rapidly under the influence of a draught of air, in consequence of the rapid evaporation of moisture from its surface, one of the benefits of draining is thus very cheaply acquired; and for the denser clays it may possibly be a desirable thing to do, but in the porous soils it would appear that no advantage is gained by it."

Yet, notwithstanding this summary disposition of the question in England, it is by no means clear, that in the tropical heat of American summers, when the difference between the temperature of the air and the subsoil is so much greater than it can ever be in England, and when we suffer from severer droughts than are common there, we may not find substantial practical advantage from the passage of these air currents through the soil.

We are not aware of experiments in America, accurate enough to be quoted as authority on the subject.