sometimes being considerable) absorb very large amounts of solar radiations of certain wave-lengths.

Movements.

The atmosphere contains, approximately, 6,166,415,570,382,815 tons of air, and 3,854,009,731,500 tons of water, the latter being very roughly calculated.

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We have found that the solar radiations pass through this in considerable proportion without much effect upon it, and their energy is expended in heating the surface of the earth and the lower atmosphere. The heat thus received per square foot of the earth's surface, one calorie 772 foot pounds, is 83 foot-pounds per second under direct rays of sun; or is equal to the work of a one-horse power engine on every six square feet or taking the whole surface, parts of which are variously inclined to the solar rays and half of which, at any instant, is receiving no rays, is equal to one-horse power engine for every fifty square feet of the earth's surface working constantly. Part of this inconceivable quantity of work is spent in the growth of vegetation; another part, probably, in the production of magnetic and electrical actions; another part of it is spent in evaporating water from the surface of the land, oceans, lakes, etc., to the amount of hundreds of billions of tons annually, the evaporation of each ton requiring nearly two million calories of heat; other parts may be spent in ways we know not of; but finally there is a great amount of this heat energy expended in putting the several quadrillions of tons of air and vapor in the atmosphere into continual and sometimes violent move

ments.

As indicated above, at any instant of time the quantity of energy per square foot being received differs greatly over the earth's surface; and as the hours of the day and the seasons of the year change, the amount received at any given place is also continually changing. Thus the air is being continually lifted up against gravity and let down and this action varies in rate and amount from place to place over the earth. This, the elastic reactions of the portions of the air on each other, the rotary motion of the earth, and other causes, combine to keep the atmosphere in continual movements. Some of these are quite regular and periodic, others very irregular. The great excess of energy received in the equatorial regions at all times causes a continuous uprising of the air; the air from both sides flowing in to supply the place of that ascending, and in turn ascending, also, to flow over toward the polar regions, sink toward the earth, and again flow into the equatorial zone to re-ascend. This quite regular general movement is shown in Fig. 16 by the direction of the arrows. The upper current toward the poles divides about latitude 35° N. and 30° S., part descending and continuing toward the poles as surface currents; the return currents from the poles to 35° N. and 30° S. lying between these upper and lower polar currents. In the neighborhood of 35° N. and 30 S. there is a region of quite variable surface movement of the air according as the one or the other surface current advances or recedes, or they become mixed, with continual irregular fluctuations. The effect of the upward movement of the air near the equator and of the downward movement of a part of it near 35° N. and 30° S. on the mean atmospheric pressure is seen in the curve of mean pressure, Fig. 6. While this general movement is going on, the earth is turning around its axis, carrying the atmosphere with it, and thus the air mov6 BD. AG.

ing toward the equator is constantly passing over regions moving more rapidly to the eastward than it is doing. This causes what would be south and north currents to become currents toward the south-west and north-west, Fig. 16. And beyond 35° N. and 30° S., where the air is constantly passing over regions moving to the east less rapidly than itself, the currents become toward the north east and the southeast.

Bearing in mind the general movement described, let a region of a few hundred square miles (Fig. 16) be excessively heated, making a very strong upward movement of the air, and inrush of air from around this place. The inward movement from all directions, combined with the general movement, produces a rotation counter-clockwise, as shown by the curved arrows. Thus a circular motion is given to a body of air of fifty, a hundred, perhaps two hundred, miles radius. This is a cyclone. The barometer is very low in its center; the upward movement considerably diminishes the atmospheric pressure. The heated air, often very moist, rising here. cools both by expansion and removal from the earth, and much of its vapor is condensed and falls as rain. This great rotating mass, in the midst of the southwesterly moving atmosphere, and on the rotating globe. is forced, according to well-known dynamical laws, to move along a curved path bearing north-westward, until it reaches the region of north-eastern movement, when its path turns in a curve to the north-east. Cyclones may start-originate-farther from the equator, even to the northward of 35°, and pursue but a part of the curved path. They gradually lose their rotary movement by friction with the surrounding mass of air and from other causes.

It follows that from about 35° N. up to pretty high latitudes, as in the United States, cyclones (the large storms that last several days) move north-easterly, or almost eastward, as up the Atlantic coast, just inland, or a little out at sea, and going off eastward over the Atlantic. Those originating in a higher latitude, as the upper Mississippi valley or Montana, move nearly eastward, a little tendency northward, and, if not spent, go off upon the Atlantic. The local physical features of the earth, mountains, large bodies of water, deserts, large forests, etc., vary, to some extent, the paths of cyclones.

Take, now, one of these cyclones (Fig. 17) moving easterly, as indicated by the large arrows E E E. Simultaneous observations of the direction and velocity of the wind always show, in a general way, the conditions represented in Fig. 17. In the region immediately surrounding the cyclone is the anti-cyclone, where the wind is blowing in all directions away from the cyclone, and is usually quite moderate in velocity. Then there is a circular region of very little movement (and high pressure, barometer). Within this is the cyclone, the wind from every direction blowing inward, with increasing velocity nearer the center, as indicated by the longer arrows, but nearly null in the central space. At a place located on the line of the upper arrow, E, the storm, preceded usually by a wind to the south-east, begins with a wind to the north-west, or nearly west, changing to a wind to the southward. At a place on the line of the central path of the cyclone, after a wind from the north-west usually, the storm begins with the wind from the south-east, with comparative calm following (as the center passes over), and then wind from the north-west. At a place so situated that the southern portion of the cyclone passes over it, after a northerly wind usually, the storm begins with wind from south

east or south, and the wind changes (going clockwise) to south, southwest, west or north-west. The north and south diameter of a cyclone is usually greater than the east and west diameter, and the outline irregular.

The water which falls as rain at any place during the passage over it of a cyclone may have been evaporated from any large bodies of water (or much even from large forests or regions of heavy vegetation) lying in any direction, or at almost any distance, from the place of falling. Once in the air as vapor the winds may carry it first in one direction and then another, for small or for great distances, till finally caught in the cyclonic movement and attendant conditions it is precipitated as rain.

The atmospheric movements, maintained by the energy received in the solar radiations, are the great transporting agencies whereby the oceans, first lifted in the air also by solar energies, are continually carried over the continents to supply the vast demand of all the organic life of the world. Nor is it alone an ocean of water continually lifted by the sunbeams, transported by sun-impelled winds and ærial movements, and falling on all the land to water the earth that it may bud and bring forth. A ton of water, evaporated by equatorial heat, holds in its vapor an added energy, which is carried with the ton of vapor, and when this is condensed into water (rain) is given out as heat-about two million calories, or units of heat, as above defined. The evaporation of millions of tons of water daily in equatorial regions, where heat is received in excess, and the transportation of a considerable portion of this vapor to descend in rains in higher latitudes, where heat may be received insufficiently, is a system of heatcarriage and supply that would exhaust the mines and forests of the earth, and all the shipping and railroads of the nations in an incalculably short time. By it temperate climates and the productive area of the earth are greatly enlarged.

Little, if at all, can we control meteorological conditions and actions; but a knowledwe of the principles and laws of this domain may enable us to so manage and conduct our affairs that they shall work for us and not against us, and that we may do intelligently and efficiently our little part of working together with the Infinite Power in making the earth yield abundantly all that contributes to our physi cal and rational well-being.

SUGGESTIONS IN RELATION TO FORESTRY.

By Prof. W. A. BUCKHOUT, State College.

[Read at Bellefonte meeting.]

It is often said, to the reproach of those who advocate an interest in forestry, that they have nothing practical to offer or suggest, that they are mere alarmists painting in vivid colors the death and destruction which are to follow when our forests and our timber are gone, but that they totally fail when they undertake to devise practical means for averting the calamity which is to come. While I do not believe that the objection is well founded, it evidently behooves the advocates of forestry to step forward and present their case in as strong a light as possible. In brief, that case is this: The marvelous rapidity in the

increase of our population, and the consequent demand for lumber and wood, for various purposes, are making such drafts upon our timber lands that it will not be long before the supply will be exhausted in all the old settled parts of the country. The natural process of reforesting is so slow and uncertain that but little value can be derived from it unless it is supplemented by the fostering care of man.

Besides their direct commercial value, forests are of marked benefit in that they are the most efficient conservators of our water supply that it is possible to have. I do not refer to the much disputed questions of the effect which forests have upon the absolute amount of rain which falls, but to the protection which they give to our streams, and to the conservation of our water supply in its general sense. Regarding this I think there is no doubt.

If, then, forests have this double function of supplying one of the most useful of the raw productions of the country, and of regulating its water distribution, what can be done toward keeping them in the most serviceable condition?

There are two ways: First, to allow and encourage by care and attention a second growth of timber; and second, to plant trees in large numbers, in other words to raise a forest as one would raise any crop. To both methods there are several difficulties, the chief of which are that trees at best grow so slowly that they can scarcely be compared with ordinary farm crops or even crops of fruit, and so long a time is required before reaching a usable size, that they are subject to many and peculiar dangers; moreover, there is a possibility that the ingenuity of man, and discoveries yet to be made, may make the forest products of much less value than they now are. This looking forward into the distant future (distant to us I mean) is not an easy matter, but it seems scarcely possible for the peculiar protective agency of forests to be supplied by any other means than by the forests themselves.

If, then, we grant that the probabilities are all in favor of the perpetual need of forests, what more can be done towards their production than nature is doing alone.

We find that as a very frequent rule second growth trees are not of the same kind as the original; that a pine forest is succeeded by some less desirable species, and, moreover, the trees, whatever they are, are very often so few that they not only do not make rapid headway against the bushes and weeds, but that they tend to develop side limbs too much, and fail to make long, straight trunks, such as in later life will make the clear stuff, free from knots, which marks the best lumber; hence nature's process of re-foresting must be supplemented very much by man's effort. How practicable it may be to sow seeds of forest trees, or to transplant trees on a large scale, can never be known except by trial. There are some cases on record by which we can get a partial knowledge of results obtained within a limited time; not so complete as it is desirable to have, nor so conclusive; since, while they show unmistakably that forests can be raised by planting seeds or young trees, they do not satisfy us as to the best and cheapest methods for doing the work in mountainous regions like our own. It is not best to enter into consideration of these cases now, further than to say that they comprise planting under a considerable variety of conditions, in poor soil and in good soil, on shifting sands and on rocky hillsides, and in different parts of the country.

The few suggestions which I have to make are based chiefly upon

observation of some cases of natural second growth timber which is for some reason much better than the average.

I

It was twenty-one years ago that I first saw a small tract of second growth white pine on what we call the barrens in this county. much regret that I did not then have sufficient forethought to measure the trees and make some estimate of the number upon a given area. I only remember that I was attracted by the vigor of the trees, their closeness, and the evident struggle which they were making with one another to see which would survive. They covered the ground to the exclusion of everything else; their trunks had already become divested of living branches below, and their tops made a canopy through which but little light fell.

At the present time this little tract still stands out in marked contrast to the mixed oak and pine about it. The trees are, of course, much fewer in number, but would still attract attention because of their symmetry, their closeness and the rapidity with which they are growing into first class timber. They average sixty feet high. Their boles are clean of limbs below, and for quite a distance further there are no living limbs, only the remnant of dead ones which are slowly dropping to the ground. Where no cutting has been done they still stand remarkably close, averaging five to the square rod, and measures near the base eight to fifteen inches in diameter. They still shade the ground so completely that but little undergrowth of any kind is. possible. But few trees have been cut except such as were under eight inches in diameter, and hence were nearly crowded out and could not have held their places much longer.

By counting the rings of growth, these trees appear to be about forty years old, and as this seems to correspond with the recollection of the few persons who know their history, I think we may assume that this is very near to their correct age. At the present time they appear to be making not more than a quarter of an inch a year, while in the first ten or fifteen years they sometimes made one-half of an inch a year. But I was not able to find live, fresh stumps, nor stumps of the largest trees, by which to get accurate figures of this kind. It is certain, however, that the present rate of growth is comparatively slow.

I have tried to have practical lumbermen give me the value per acre of this young timber, but on account of the small size of the trees, which units them for general use, the most that can be said is that it is growing in value all the while, and is worth more to hold than for present use; if used now it would cut very much to waste, and is suitable only for a few purposes. Forty years ago then, this small tract of land received a shower of white pine seed from some old trees -a single one of these trees some four feet in diameter is still standing, and numerous old stumps and logs attest to the presence of others. Favoring conditions permitted a very large number of these seeds to germinate, and probably the young trees stood not far from one to the square foot of ground at the time when they obtained sole possession. Having gained this one point, complete possession, they entered upon a race and a battle with one another, and that is still going on, and will not end until the axe or fire of the lumbermen sweep them away. Such cases as these ought to be of special value in teaching us that what nature does so successfully by her own unaided efforts may be done fully as well, and upon a much larger scale, where the intelligent efforts of man shall be added. Brought down to a practical sug