The new air world

by Willis L. Moore

Soil Usually Warmer Than Air Next Above. In summer, June to August, the bare, dry, top soil is warmer than the air ten feet above during all hours of the day and night, at times the difference being as much as forty degrees at midday. During winter, December to February, it is slightly cooler, except between 9 A.M. and 3 P.M. when the excess is seldom more than ten degrees. Evaporation from a wet soil lowers its temperature below that of the air immediately above through the rendering latent of a large quantity of heat. A melting snow surface also is below the temperature of the air because of the heat employed in changing the snow to the liquid form.

Let Mother Earth Cool and Refresh You During the Heat of Summer. How little the average man realizes the possibilities for improving his condition that lie close at hand. He does not know, or he is indifferent to the fact, that only three feet from the surface of the ground it is as cool at midday as at midnight, and that there is no diurnal variation in temperature below that depth, and no annual variation below a depth of from thirty to forty feet. If one were to set down the temperature of each day, add the numbers at the end of the year, and divide the sum by 365 the quotient would equal the temperature always found at that place at a depth of about thirty feet. The temperature of a deep-flowing spring is always about the mean annual air temperature of the place. Here is health-giving coolness for summer and warmth for winter of which one takes little heed and derives practically no profit.

Remarkable, is it not? And these beneficent conditions are universal and available for all, except to those crowded into congested centers of population. The temperature is 54° in the Mammoth Cave in Kentucky and shows no change from day to day and from winter to summer.

During the extreme heat of summer and the cold of winter many could profitably, healthfully, and pleasantly live below ground. During such periods the cellar of the house, which should be deep and spacious, even extending beyond the dimensions of the edifice above, if a continuous supply of pure air could be forced through it, or natural ventilation accomplished by the plan outlined below, should be the lounging, resting, and sleeping place of the occupants of the household. It is not impossible or extremely difficult to change the stagnant, moist, germ-laden, ill-smelling air of the average cellar, in which it is positively dangerous to spend much time, into active, pure, and delightfully healthful air,—air in which the worn and weary worker from the heat of the farmer’s field, or the artisan and the clerk from the debilitating temperatures of the factory and the office could recuperate from the toil of the day, and from which they would go forth each morning invigorated for another day’s efficient service, instead of dragging weary limbs from hot, sleepless beds, each morning less in energy than the day before. As is shown in other parts of this book, the researches of Huntington have proven conclusively that man is at his lowest physical and mental points of efficiency, and more subject to the contraction of disease through weakness, in midsummer and midwinter, and that the hotter the summer and the colder the winter the less is his energy and the lower is his power of resistance.

The whole problem is one of ventilation. While this is simple, it must be scientifically done. The ideal location for a living cellar is a hillside. It is easy to install ventilators in the roof of a cellar no matter where located, but these are of no avail whatever if there is not adequate air drainage at the bottom of the cellar. From the cellar in a hillside a conduit can lead from the bottom of the inclosure and have its opening at a lower level, thereby accomplishing drainage and circulation, which are all-important in the creating of a sanitary condition of air under the cool earth. For each thousand cubic feet of cellar space there should project from the roof, to a height of at least six feet above ground, a separate ventilator shaft of at least one square foot cross-section dimension. A like ventilating capacity should be provided from the bottom outward to a lower level, but here two or more shafts may be combined in one, so the proper capacity is secured. During the day the draft will be upward through this system. But at night, except when the wind is brisk, the direction of movement of the air is reversed, and the cool air of the minimum temperature of night or early morning, because of its greater density, drops down into the cellar. The drainage shaft should be provided with a damper, which should be closed in the early morning, about daybreak, entrapping the cold air of night. The lower opening should be covered with wire netting, to exclude small animals, and the whole construction be of concrete, rendering it imperishable and rat-proof.

Inexpensive but Efficient Cold Storage. Such a sanitary cellar as described above provides an excellent storage for fruits and vegetables, comparing favorably with the much more expensive artificial refrigeration. By an intelligent manipulation of the damper in the lower shaft, cool storage may be provided for fruit and other produce in the early fall, and protection secured against the extreme cold of winter.

Why Does Air Cool with Ascent and Heat with Descent? If a mass of air be elevated 183 feet it will be found to have lost one degree in temperature, because there is less air above to exert pressure upon it and it therefore expands to greater volume, and in the process of expansion work is performed which employs heat and renders it latent. One minute, one hour, or a thousand years thereafter, if this same air be lowered to its former elevation, it will be compressed into its previous dimensions and the heat energy that formerly was employed to expand it will be restored to the sensible condition. This ratio of 183 feet to one degree does not hold for any extended movement, because, as soon as the dew point of the air is reached, condensation in the form of cloud or rain occurs and the heat of condensation is released; that is to say, the same quantity of heat employed to create the water vapor at some previous time and thereby rendered latent is now become sensible and partly makes up for the loss by expansion as the air ascends. The average is therefore about three hundred feet for one degree.

Height of Freezing Cold in the Free Air. The frost level remains constant, winter and summer, over the equator at about eighteen thousand feet. Elsewhere this level rises and falls with the seasons, the amplitude of the movement increasing with latitude and being greater over land than over water on the same parallel.

Daily Range of Temperature in the Free Air. The difference between the temperature of day and that of night decreases with altitude in the free air and ceases at about eight thousand feet. It is greatest during clear weather and least in cloudy weather. Narrow valleys may show a greater daily range than hilltops. When the sky is clear, radiation from the hillsides may heat the air in a valley to almost furnace heat at midday, while at night the air, coming in contact with cool vegetation higher up, chills and, gaining in weight by contraction, flows down and collects in the valley, making the bottom of the valley warmer during day and colder during night than the air above. Often moisture-laden winds precipitate much of their water vapor as the air cools by expansion in passing over a mountain range. These winds carry a comparatively dry air over to the leeward side of the mountain, where the daily range of temperature will be much greater than on the windward side at the same elevation. San Francisco, where the prevailing winds come from the ocean, has a less range than New York, where the predominating winds are from the land; but New York is influenced by its proximity to the ocean, for its range is much less than at Denver, in the interior of the continent. The range is less on the east side of Lake Michigan than on the west side, as it is with relation to all similar bodies of water.