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Up to the year 1846, when Leverrier made his great discovery, it was believed that Uranus was the most distant planet revolving around the sun. Uranus itself was discovered by Sir John Herschel in England in the year 1781. As this planet takes eighty-four years to go round the sun, its complete revolution had not yet been observed in 1846; in spite of this, however, the course of Uranus was calculated and known very precisely, because the attractive force of the sun was known; and all the disturbances that might influence the planet were taken into account.

But notwithstanding all nicety of calculations, the real course of Uranus would not at all agree with the one computed. At that time already, long before Leverrier's discovery, the idea arose that beyond Uranus, in a region where the human eye could, in spite of all telescopes, discover nothing, there must probably exist a planet which changed the course of Uranus. Bessel, a great astronomer, who unfortunately for science died too soon, was already on the point of finding out by computation the unknown disturber. But he died, shortly before Leverrier's discovery. As early even as 1840, Maedler, in the city of Dorpat, in Russia, wrote a fine article on this as yet unseen disturber.

Leverrier, however, began the task and finished it. He computed with an acuteness that was admired by all men of science. He investigated whereabout in the heavens that intruder must be situated, so as to be able to trouble Uranus to such an extent; how fast this disturber itself must move in its orbit, and how large must be its mass.

We live to see the triumph of Leverrier's being able to discover with his mental eye, by means of computation only, a planet at a distance of millions of miles from him.

Therefore let us say: Honor science! Honor the men that cultivate it! And all honor to the human intellect which sees farther than the human eye!

PART VI.

METEOROLOGY

CHAPTER I.

SOMETHING ABOUT THE WEATHER

We presume that in a state of unusual bad weather there are many persons, who find occasion to reflect on the nature of weather in general.

A few years ago, we had "green Christmas and white Easter," and spring was of course far behind when Pentecost arrived. We had still cold and rainy days, while the nights were frosty; and, if one might judge from appearances, it seemed that nature had made a mistake, and had not known of our being then in the month of June, which, with us, is usually a delightful month.

The sun alone was right. He rose on the 9th of June of that year precisely at 4 o'clock 30 minutes, as was prescribed to him by the calendar; and set at 7 o'clock 30 minutes, precisely according to orders. At that time the sun was hastening towards summer, he lengthened the days and shortened the nights; but he alone is not capable of governing the weather, and our friends the astronomers, although they are able to calculate the sun's course with more precision than the engineer can the locomotive's, are themselves greatly embarrassed when asked, "What kind of weather shall we have the day after to-morrow?"

It is unpardonable that some of our almanacs, especially those for the farmer, contain prophecies about the weather. We cannot be too indignant against the foolish superstition which this abuse tends to foster. And what is worse, really shameful, is, that those who print such things do not believe in them themselves, but consider them a necessity sanctioned by age and custom, and offer it as such to the credulity of the public.

The subject of this article on the knowledge of weather, is a science, a great branch of the natural sciences; but it is a branch just developing, and therefore has, up to the present time, not yet brought forth any fruit.

It is very likely that at some future day we shall be able to indicate in advance the weather of any given place. But for the present this is impossible; and if from time to time men arise and announce that they can calculate and determine in advance the state of the weather in any given place – pretending to consult the planets, etc. – we take it for granted that they are as unreliable as the weather-prophets of the almanacs.

We said above that the weather might possibly be determined a few days ahead; science is at present almost far enough advanced for it. But there are needed for that purpose grand institutions, which must first be called into life.

If for the proper observation of the weather, stations were erected throughout the extent of our country, at a distance of about seventy miles from each other, and if these stations were connected by a telegraph-wire, managed by a scientific reliable observer; then we might, in the middle portion of our country, be able to determine in advance the state of the weather, though for a short time only.

For the changeableness of the weather depends on the nature and motion of the air, and on the amount of moisture, and the direction of the winds. It is mostly occasioned by currents of air which pass over the earth, producing, wherever they meet, here cold, there heat – here rain, there hail or snow.

Along a part of the coast of the United States electric telegraphs have been established. Vessels receive, at a considerable distance, the news of a storm approaching, together with its velocity and direction. The electric telegraph being quicker than the wind, the vessels receive the news in time to take their directions. Before the storm reaches them, they have been enabled to take precautionary measures for its reception.

This is a great step forward in our new science. But not before the time when such stations shall be established everywhere throughout the land, will meteorology manifest its real importance. For it has, like every other science, firmly established rules, which can easily be calculated and verified; while, on the other hand, allowances must be made for changeable conditions which tend to disturb the rules.

We will now endeavor to introduce to our readers these established rules, and explain the changeable conditions to which we refer.

CHAPTER II.

OF THE WEATHER IN SUMMER AND WINTER

As we have stated above, there exist fixed rules about the weather; these rules are simple and easy to compute. But our computations are often disturbed by a great many circumstances beyond our reach, so much that we are governed more by exceptions than rules.

These latter are based on the position of our earth with regard to the sun. They are, therefore, easy to determine, for astronomy is a science resting on firm pillars; and although nothing in the universe is so far from us as the stars, yet there is nothing in the world so certain as our knowledge of the courses of the constellations and their distances. Many of our readers may be surprised, perhaps, to hear that we know more accurately the distance from the earth to the sun than the distance from New York to Cincinnati. Indeed, astronomical knowledge is the most reliable in the world. No merchant is able to measure a piece of cloth without being mistaken, to say the least, as much as 1/300 part; while the uncertainty with respect to distances of bodies in the solar system amounts to a great deal less than 1/300 part.

Our earth turns on its axis once in every twenty-four hours, and goes also round the sun once a year. But the earth's axis is inclined towards the earth's orbit – orbit is the circle which a celestial body describes in its revolution around another – in such a manner as to cause the earth, in its orbit round the sun, to be illuminated for six months on one side, and for six months on the other side of the earth. Hence it happens, that at the north pole there is continual day during six months in the year, after which follows uninterrupted winter for the next six months; in the same way the day on the south pole lasts six months, and the night following the same length of time. In the middle between both poles, however, in the regions around the equator, the day has throughout the year twelve hours; the night, of course, the same; while in the countries between the equator and the poles, the length of day and night is, through the whole year, constantly varying.

We, in the United States, inhabit the northern hemisphere; when, therefore, the time comes that the north pole has day for six months, we in North America, being situated about half-way between the equator and north pole, enjoy long days and short nights. The inhabitants of those countries, however, situated on the southern hemisphere, have at that time short days and long nights. But when the time comes that there is six months' night on the north pole and six months' day on the south pole, then will the inhabitants of the southern hemisphere have long days, and we long nights.

Intimately connected with the length of day and night are our seasons, especially summer and winter; for together with the sun's light heat is also called forth. During our long days, therefore, it is very warm with us, for the sun's rays heat the soil. During our short days we experience cold, because the warming light of the sun does not reach our earth directly. For this reason the northern hemisphere enjoys summer while the southern has winter; and vice versâ, when we have mid-winter, people in the other hemisphere are in the midst of summer. When we are snowed up at Christmas, and seek joy and elevation by the cheerful fireside in the brightly-lighted room, we may, perhaps, think of our friends and relatives who have emigrated to Australia, and the question may occur to us, how things may be with them this cold weather, and how they are enjoying the holidays?

Now, would not the uninformed be surprised, if a letter were to arrive from Australia, written at Christmas, telling how the writer enjoyed Christmas in his vine-arbor, where he had sought shelter from the terrible heat of the day, and that he had but late at night gone to his room, and he could scarcely sleep then on account of the heat, and the longing for his former home in the United States, where he could always enjoy cool weather at Christmas.

The uninformed will now learn that Australia lies in the southern hemisphere, while we are in the northern, and that there they live in midst of summer, while we are buried in snow. Nor will he now be surprised when he reads, that it snowed in Australia in the month of August, and that his friend or relative there reposed by the fireside, and read the letter from home by the light of the lamp, at the same hour that we here were taking an afternoon walk in the summer shade.

The heat of summer, however, does not altogether depend upon the length of the day; nor does the cold of winter upon its shortness; but principally on this, that during summer-time the sun at noon stands directly over head; that therefore his vertical rays are enabled to pierce the soil with intense heat; while in winter-time the sun at noon stands nearer to the horizon; his rays fall on the earth obliquely, therefore heating the soil with but feeble power.

We shall presently see that this position of the sun exercises great influence upon the weather.

CHAPTER III.

THE CURRENTS OF AIR AND THE WEATHER

In order to fully understand the conditions of the atmosphere, one must carefully notice the following:

Though the sun produces summer and winter, and although his beams call forth heat, and the absence of heat causes intense cold on the surface of the globe, yet the sun alone does not make what we call "Weather."

If the sun's influence alone were prevalent, there would be no change at all during our seasons; once cold or warm, it would invariably continue to be so, according to the time of the year. The sun, however, produces certain movements in the air; currents of air or winds pour from cold countries into warm ones, and vice versâ from warm ones into cold ones. It is this that makes our sky be cloudy or clear; that produces rain and sunshine, snow and hail, refreshing coolness in summer and warmth sometimes in midwinter, as also chilly nights in summer and thaw in winter. In other words, it is more properly the motion of the air, the wind, that produces what we call weather; that is, that changeableness from heat to cold, from dryness to moisture, all of which may be comprised in one name, weather.

But whence does the wind arise? It is caused by the influence of the sun's heat upon the air.

The whole earth is enveloped with a misty cover called "air." This air has the peculiar quality of expanding when it becomes heated. If you put a bladder that is filled with air and tied up, into the pipe of a heated stove, the air inside will expand so much as to burst the bladder with a loud report. The warm expanded air is lighter than the cold air, and always ascends in the atmosphere.

Lofty rooms are therefore difficult to heat because the warm air ascends towards the ceiling. In every room it is much cooler near the floor than near the top of the room. This accounts for the singular fact that in winter our feet, though warmly clad in stockings and shoes or boots, feel cold more often than our hands, which are entirely uncovered. If you ascend a ladder in a tolerably cold room, you are surprised at finding it much warmer above than below in the room. The flies take advantage of this in autumn, when they are seen to promenade on the ceiling, because there it is warm as in summer, while near the floor it is cold; owing to the circumstance that warm air, being lighter than cold, ascends.

Precisely the same takes place on the earth. In the hot zone near the equator the sun heats the air continually; hence the air there ascends. But from both the northern and southern hemispheres, cold air is constantly pouring towards the equator in order to fill the vacuum thus produced. This cold air is now heated also and rises, while other cold air rushes in after. By this continued motion of the air towards the equator, however, a vacuum is created also at both poles of the earth; and the heated air of the equator, after having ascended, flows towards these two vacuums. Thus arise the currents in the air; currents which continue the whole year, and cause the cold air to move from the poles to the equator along the surface of the earth; while higher in the atmosphere the heated air flows from the equator back to the poles.

Therefore the air is said to circulate below from the poles to the equator, but above to go back from the equator to the poles.

He who is in the habit of noticing phenomena of nature, may often have observed something of the kind when opening the window of a room filled with smoke. The smoke escapes above, while below it seems to come back into the room again.

But this is an illusion which has its origin in the fact, that above the warm air of the room goes out of the window, and, of course, takes the smoke with it; below at the window, however, cold air pours in from without, driving the smoke that is below back into the room. The attentive observer may also see how the two currents of air above and below move in contrary directions; while in the middle part they repel each other, and form a kind of eddy which may be clearly perceived by the motion of the smoke.

What takes place on our earth is nothing different from this, and we shall presently see the great influence this has upon our weather.

CHAPTER IV.

THE FIRM RULES OF METEOROLOGY

The air which is continually rising in the hot zones and circulating towards the poles and back again to the equator, is the prime source of the wind. This latter modifies the temperature of the atmosphere; for the cold air from the poles of the earth, in coming to the equator, cools the torrid zone; again, the hot air going from there to the poles heats the colder regions. This accounts for the fact that very often it is not so cold in cold countries as it really would be, were it not for this circulation of the air; and that in hot countries we never find the degree of heat that there would be if the air were continually at rest.

According to what has been said, however, but two different winds would exist on the earth, and these two moving in fixed directions; one sweeping over the earth from the poles to the equator, with us called "North wind," and one from the equator to the icy regions, with us the "South wind."

But we must add here something which considerably modifies this, viz., the revolution of the globe. The earth, it is well known, revolves round its axis from west to east once in twenty-four hours; the atmosphere performs this revolution also.

But since that part of the atmosphere nearest to the equator must move with greater velocity than the part nearer the poles, it may with a little thinking be easily understood, that the air which goes on the surface of the earth from the poles to the equator, passes over ground which moves faster east than the air itself; while, on the contrary, the air coming from the hot zone starts in an eastern direction with the velocity it had on the equator; but, as it is moving on, it passes over that part of the earth which rotates with less velocity.

This gives rise to what are called the trade-winds, so very important to navigation. In our hemisphere the trade-winds come in the lower strata of the air from the northeast; while in the upper strata they move towards northeast, they come from the southwest. On the other hemisphere the trade-winds in the lower strata of the air move in a northwesterly direction; in the upper they move in a southeasterly direction.

From this arise our rules respecting the weather.

The idea that many persons have that wind and weather are two things entirely different, is wrong. Weather is nothing else but a condition of the atmosphere. A cold winter, cold spring, cold summer, and cold autumn, do not mean, as some believe, that the earth, or that part of it on which they live, is colder than usual; for if we dig a hole in the ground, it will be found that neither cold nor warm weather has any influence upon the temperature below the surface of the earth. At the small depth of thirty inches below the surface, no difference can be found between the heat of the day and the cold of the night. In a well sixty feet deep no difference is perceivable between the hottest summer and the coldest winter-day, for below the surface of the earth the differences of temperature do not exist. What we call Weather is but a state of the atmosphere, and depends solely upon the wind.

It has been stated already that there are fixed rules of weather, or, which is the same thing, that there are laws governing the motion of the winds; but we have added also, that there are a great many causes which disturb these rules, and therefore make any calculations in advance a sheer impossibility.

We have seen that these rules are called forth, 1st, by the course of the sun; 2d, by the circulation of the air from the poles to the equator and back again; and 3d, by the revolution of the earth, causing the trade-winds.

All these various items have been calculated correctly; and, owing to this, we have now a firm basis in meteorology. But in the next article, we shall see what obstacles are put in the way of this new science by other things; and the allowances to be made for these disturbances cannot be easily computed.

CHAPTER V.

AIR AND WATER IN THEIR RELATIONS TO WEATHER

Let us now examine the causes which disturb the regular currents of air, and which render the otherwise computable winds incomputable, thus producing the great irregularities of the weather.

The main cause lies in this, that neither the air nor the earth is everywhere in the same condition.

Every housewife that but once in her life hung up clothes to dry, knows full well that air absorbs moisture when passing over, or through, wet objects. If she wishes to dry her clothes very quickly, she will hang them up where there is much wind. And she is perfectly right in maintaining that the wind dries clothes better than the quiet sunshine.

Whence does this come?

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.

Hence, it is not heat alone that causes the clothes to dry; for in winter-time, though it is so cold that the clothes on the line freeze to stiffness, they dry nevertheless, if it be very windy. It is the wind which dries them by allowing fresh air to pass through them continually. For the same reason our housewives open doors and windows after a room has been scoured, so that by a thorough draft of air, the floor may dry quickly; a large fire in the stove or fireplace could not effect it so readily.

From all this we may learn that the air absorbs particles of water. It will now be evident to every one, why water in a tumbler, standing uncovered at the open window for a few days, constantly decreases, until it finally disappears entirely and the tumbler is dry. Where has the water gone? The air drank it off, little by little, until at last the tumbler was emptied.

"But," you will exclaim, "what does the air do with all the water it drinks? The air goes over the whole ocean; over lakes, rivers, brooks, and springs; over woods and fields, and everywhere it takes in particles of water. What becomes of them?"

After being absorbed, the particles of water unite and form clouds; then they fall down in the form of fog, rain, snow, or hail.

Many persons, even highly educated ones, have false ideas about these phenomena of the atmosphere.

Some think a cloud is a kind of bag that contains the rain which is let fall by the cloud. This is entirely false. The clouds are nothing but fogs in the upper regions of the atmosphere; fog itself is nothing but a cloud immediately over ground.

It is easy to obtain a correct idea of the formation of fog and rain; one need but observe for one's self.

He who has ever blown upon his hands in winter-time in order to warm them, will have observed that his hands become moist from his breath. If a window-pane is breathed upon, it is covered by a thin coat of water. What is the cause of this? It arises from the fact that the air we exhale contains water-particles from our blood. We do not see them when it is warm, because they are airy themselves; everybody knows that they become visible so soon as the air turns cool; or that they appear like fog when one is in a cold room in winter; that they form drops when you breathe upon cold objects; that they freeze and become snow; nay, that in severe cold weather, after a long walk outdoors, they even cling to one's moustache like icicles.

This may illustrate, that these particles of water are invisible in the warm air, but that when the air is colder they appear as fog; when still colder, as drops of rain; and in very cold weather they turn to snow, while in severe cold they freeze and form ice.

CHAPTER VI.

FOG, CLOUDS, RAIN, AND SNOW

The air imbibes particles of water from all parts of the earth; and thus charged with water it is the same and operates the same as our breath.

So soon as a stratum of air that contains water-particles, meets with a colder stratum, these airy particles of water immediately flow together to form fog. But fog, as has been said, is nothing but a cloud. He who has travelled in mountainous countries, has often noticed this. From the valley it often appears that the top of a high mountain is wrapped in clouds; and his curiosity may be excited to ascend the mountain in order to examine these clouds. But when he arrives there, he sees nothing whatever either before or behind him but fog, which most assuredly he has often seen before without so much trouble. The ignorant person who believes that a cloud is something else than fog, and who fancies that the clouds which he saw from below have disappeared during his ascent, leaving but a mist behind, will be no little amazed when he has arrived at the foot of the mountain again, to see the cloud above as before, and to perceive that he actually walked among the clouds.