“It is indeed,” says good Bishop Berkeley, “an opinion strangely prevailing amongst men that ... all sensible objects have an existence ... distinct from their being perceived by the understanding. But ... some truths there are, so near and obvious to the mind, that a man need only open his eyes to see them. Such I take this important one to be, namely, that all the choir of heaven and furniture of the earth—in a word, all those bodies which compose the mighty frame of the world—have not any subsistence without a mind.”

We are not going to take the reader along “the high priori road” of metaphysics, but only to speak of certain accepted conclusions of modern experimental physics, which do not themselves, indeed, justify all of Berkeley’s language, but to which these words of the author of “A New Theory of Vision” seem to be a not unfit prelude.

When we see a rose-leaf, we see with it what we call a color, and we are apt to think it is in the rose. But the color is in us, for it is a sensation which something coming from the sun excites in the eye; so that if the rose-leaf were still there, there would be no color unless there were an eye to receive and a brain to interpret the sensation. Every color that is lovely in the rainbow or the flower, every hue that is vivid in a ribbon or sombre in the grave harmonies of some old Persian rug, the metallic lustre of the humming-bird or the sober imperial yellow of precious china,—all these have no existence as color apart from the seeing eye, and all have their fount and origin in the sun itself.

“Color” and “light,” then, are not, properly speaking, external things, but names given to the sensations caused by an uncomprehended something radiated from the sun, when this falls on our eyes. If this very same something falls on our face, it produces another kind of sensation, which we call “heat,” or if it falls on a thermometer it makes it rise; while if it rests long on the face it will produce yet another effect, “chemical action,” for it will tan the cheek, producing a chemical change there; or it will do the like work more promptly if it meet a photographic plate. If we bear in mind that it is the identically same thing (whatever that is) which produces all these diverse effects, we see, some of us perhaps for the first time, that “color,” “light,” “radiant heat,” “actinism,” etc., are only names given to the diverse effects of some thing, not things themselves; so that, for instance, all the splendor of color in the visible world exists only in the eye that sees it. The reader must not suppose that he is here being asked to entertain any metaphysical subtlety. We are considering a fact almost universally accepted within the last few years by physicists, who now generally admit the existence of a something coming from the sun, which is not itself light, heat, or chemical action, but of which these are effects. When we give this unknown thing a name, we call it “radiant energy.”

How it crosses the void of space we cannot be properly said to know, but all the phenomena lead us to think it is in the form of motion in some medium,—somewhat (to use an imperfect analogy) like the transmission through the air of the vibrations which will cause sound when they reach an ear. This, at any rate, is certain, that there is an action of some sort incessantly going on between us and the sun, which enables us to experience the effects of light and heat. We assume it to be a particular mode of vibration; but whatever it is, it is repeated with incomprehensible rapidity. Experiments recently made by the writer show that the slower heat vibrations which reach us from the sun succeed each other nearly 100,000,000,000,000 times in a single second, while those which make us see, have long been known to be more rapid still. These pass outward from the sun in every direction, in ever-widening spheres; and in them, so far as we know, lies the potency of life for the planet upon whose surface they fall.

Did the reader ever consider that next to the mystery of gravitation, which draws all things on the earth’s surface down, comes that mystery—not seen to be one because so familiar—of the occult force in the sunbeams which lifts things up? The incomprehensible energy of the sunbeam brought the carbon out of the air, put it together in the weed or the plant, and lifted each tree-trunk above the soil. The soil did not lift it, any more than the soil in Broadway lifted the spire of Trinity. Men brought stones there in wagons to build the church, and the sun brought the materials in its own way, and built up alike the slender shaft that sustains the grass blade and the column of the pine. If the tree or the spire fell, it would require a certain amount of work of men or horses or engines to set it up again. So much actual work, at least, the sun did in the original building; and if we consider the number of trees in the forest, we see that this alone is something great. But besides this, the sun locked up in each tree a store of energy thousands of times greater than that which was spent in merely lifting the trunk from the ground, as we may see by unlocking it again, when we burn the tree under the boiler of an engine; for it will develop a power equal to the lifting of thousands of its kind, if we choose to employ it in this way. This is so true, that the tree may fall, and turn to coal in the soil, and still keep this energy imprisoned in it,—keep it for millions of years, till the black lump under the furnace gives out, in the whirling spindles of the factory or the turning wheel of the steamboat, the energy gathered in the sunshine of the primeval world.

The most active rays in building up plant-life are said to be the yellow and orange, though Nature’s fondness for green everywhere is probably justified by some special utility. At any rate, the action of these solar rays is to decompose the products of combustion, to set free the oxygen, and to fix the carbon in the plant. Perhaps these words do not convey a definite meaning to the reader, but it is to be hoped they will, for the statement they imply is wonderful enough. Swift’s philosopher at Laputa, who had a project for extracting sunbeams out of cucumbers, was wiser than his author knew; for cucumbers, like other vegetables, are now found to be really in large part put together by sunbeams, and sunbeams, or what is scarcely distinguishable from such, could with our present scientific knowledge be extracted from cucumbers again, only the process would be too expensive to pay. The sunbeam, however, does what our wisest chemistry cannot do: it takes the burned out ashes and makes them anew into green wood; it takes the close and breathed out air, and makes it sweet and fit to breathe by means of the plant, whose food is the same as our poison. With the aid of sunlight a lily would thrive on the deadly atmosphere of the “black hole of Calcutta;” for this bane to us, we repeat, is vital air to the plant, which breathes it in through all its pores, bringing it into contact with the chlorophyl, its green blood, which is to it what the red blood is to us; doing almost everything, however, by means of the sun ray, for if this be lacking, the oxygen is no longer set free or the carbon retained, and the plant dies. This too brief statement must answer instead of a fuller description of how the sun’s energy builds up the vegetable world.

But the ox, the sheep, and the lamb feed on the vegetable, and we in turn on them (and on vegetables too); so that, though we might eat our own meals in darkness and still live, the meals themselves are provided literally at the sun’s expense, virtue having gone out of him to furnish each morsel we put in our mouths. But while he thus prepares the material for our own bodies, and while it is plain that without him we could not exist any more than the plant, the processes by which he acts grow more intricate and more obscure in our own higher organism, so that science as yet only half guesses how the sun makes us. But the making is done in some way by the sun, and so almost exclusively is every process of life.

It is not generally understood, I think, how literally true this is of every object in the organic world. In a subsequent illustration we shall see a newspaper being printed by power directly and visibly derived from the sunbeam. But all the power derived from coal, and all the power derived from human muscles, comes originally from the sun, in just as literal a sense; for the paper on which the reader’s eye rests was not only made primarily from material grown by the sun, but was stitched together by derived sun-power, and by this, also, each page was printed, so that the amount of this solar radiation expended for printing each chapter of this book could be stated with approximate accuracy in figures. To make even the reader’s hand which holds this page, or the eye which sees it, energy again went out from the sun; and in saying this I am to be understood in the plain and common meaning of the words.

Did the reader ever happen to be in a great cotton-mill, where many hundreds of operatives watched many thousands of spindles? Nothing is visible to cause the multiplied movement, the engine being perhaps away in altogether another building. Wandering from room to room, where everything is in motion derived from some unseen source, he may be arrested in his walk by a sudden cessation of the hum and bustle,—at once on the floor below, and on that above, and all around him. The simultaneousness of this stoppage at points far apart when the steam is turned off, strikes one with a sense of the intimate dependence of every complex process going on upon some remote invisible motor. The cessation is not, however, absolutely instantaneous; for the great fly-wheel, in which a trifling part of the motor power is stored, makes one or two turns more, till the energy in this also is exhausted, and all is still. The coal-beds and the forests are to the sun what the fly-wheel is to the engine: all their power comes from him; they retain a little of it in store, but very little by comparison with the original; and were the change we have already spoken of to come over the sun’s circulation,—were the solar engine disconnected from us,—we could go on perhaps a short time at the cost of this store, but when this was over it would be over with us, and all would be still here too.

Is there not a special interest for us in that New Astronomy which considers these things, and studies the sun, not only in the heavens as a star, but in its workings here, and so largely in its relations to man?

Since, then, we are the children of the sun, and our bodies a product of its rays, as much as the ephemeral insects that its heat hatches from the soil, it is a worthy problem to learn how things earthly depend upon this material ruler of our days. But although we know it does nearly all things done on the earth, and have learned a little of the way it builds up the plant, we know so little of the way it does many other things here that we are still often only able to connect the terrestrial effect with the solar cause by noting what events happen together. We are in this respect in the position of our forefathers, who had not yet learned the science of electricity, but who noted that when a flash of lightning came a clap of thunder followed, and concluded as justly as Franklin or Faraday could have done that there was a physical relation between them. Quite in this way, we who are in a like position with regard to the New Astronomy, which we hope will one day explain to us what is at present mysterious in our connection with the sun, can as yet often only infer that when certain phenomena there are followed or accompanied by others here, all are really connected as products of one cause, however dissimilar they may look, and however little we know what the real connection may be.

There is no more common inquiry than as to the influence of sun-spots on the weather; but as we do not yet know the real nature of the connection, if there be any, we can only try to find out by assembling independent records of sun-spots and of the weather here, and noticing if any changes in the one are accompanied by changes in the other; to see, for instance, if when sun-spots are plenty the weather the world over is rainy or not, or to see if when an unusual disturbance breaks out in a sun-spot any terrestrial disturbance is simultaneously noted.

When we remember how our lives depend on a certain circulation in the sun, of which the spots appear to be special examples, it is of interest not only to study the forms within them, as we have already been doing here, but to ask whether the spots themselves are present as much one year as another. The sun sometimes has numerous spots on it, and sometimes none at all; but it does not seem to have occurred to any one to see whether they had any regular period for coming or going, till Schwabe, a magistrate in a little German town, who happened to have a small telescope and a good deal of leisure, began for his own amusement to note their number every day. He commenced in 1826, and with German patience observed daily for forty years. He first found that the spots grew more numerous in 1830, when there was no single day without one; then the number declined very rapidly, till in 1833 they were about gone; then they increased in number again till 1838, then again declined; and so on, till it became evident that sun-spots do not come and go by chance, but run through a cycle of growth and disappearance, on the average about once in every eleven years. While amusing himself with his telescope, an important sequence in Nature had thus been added to our knowledge by the obscure Hofrath Schwabe, who indeed compares himself to Saul, going out to seek his father’s asses and finding a kingdom. Old records made before Schwabe’s time have since been hunted up, so that we have a fairly connected history of the sun’s surface for nearly a hundred and fifty years; and the years when spots will be plentiful or rare can now be often predicted from seeing what has been in the past. Thus I may venture to say that the spots, so frequent in 1885, will have probably nearly disappeared in 1888, and will be probably very plentiful in 1894. I do not know at all why this is likely to happen; I only know that it has repeatedly happened at corresponding periods in the past.

“Now,” it may be asked, “have these things any connection with weather changes, and is it of any practical advantage to know if they have?”

Would it be, it may be answered, of any practical interest to a merchant in bread-stuffs to have private information of a reliable character that crops the world over would be fine in 1888 and fail in 1894? The exclusive possession of such knowledge might plainly bring “wealth beyond the dreams of avarice” to the user; or, to ascend from the lower ground of personal interest to the higher aims of philanthropy and science, could we predict the harvests, we should be armed with a knowledge that might provide against coming years of famine, and make life distinctly happier and easier to hundreds of millions of toilers on the earth’s surface.

“But can we predict?” We certainly cannot till we have, at any rate, first shown that there is a connection between sun-spots and the weather. Since we know nothing of the ultimate causes involved, we can only at present, as I say, collect records of the changes there, and compare them with others of the changes here, to see if there is any significant coincidence. To avoid columns of figures, and yet to enable the reader to judge for himself in some degree of the evidence, I will give the results of some of these records represented graphically by curves, like those which he may perhaps remember to have seen used to show the fluctuations in the value of gold and grain, or of stocks in the stock-market. It is only fair to say that mathematicians used this method long before it was ever heard of by business men, and that the stockbrokers borrowed it from the astronomers, and not the astronomers from them.

In Fig. 48, from Carrington’s work, each horizontal space represents ten years of time, and the figures in the upper part represent the fluctuations of the sun-spot curve. In the middle curve, variations in vertical distances correspond to differences in the distance from the sun of the planet Jupiter, the possibility of whose influence on sun-spot periods can thus be examined. In the third and lowest, suggested by Sir William Herschel, the figures at the side are proportional to the price of wheat in the English market, rising when wheat ruled high, falling when it was cheap. In all three curves one-tenth of a horizontal spacing along the top or bottom corresponds to one year; and in this way we have at a glance the condensed result of observations and statistics for sixty years, which otherwise stated would fill volumes. The result is instructive in more ways than one. The variations of Jupiter’s distance certainly do present a striking coincidence with the changes in spot frequency, and this may indicate a real connection between the phenomena; but before we decide that it does so, we must remember that the number of cycles of change presented by the possible combination of planetary periods is all but infinite. Thus we might safely undertake, with study enough, to find a curve, depending solely on certain planetary configurations, which yet would represent with quite striking agreement for a time the rise and fall in any given railroad stock, the relative numbers of Democratic and Republican congressmen from year to year, or anything else with which the heavenly bodies have in reality as little to do. The third curve (meant by the price of wheat to test the possible influence of sun-spots on years of good or bad harvests) is not open to the last objection, but involves a fallacy of another kind. In fact the price of wheat depends on many things quite apart from the operations of Nature,—on wars and legislation, for instance; and here the great rise in the first years of the century is as clearly connected with the great continental wars of the first Napoleon, which shut up foreign ports, as the sudden fall about 1815, the year of Waterloo, is with the subsequent peace. Meanwhile an immense amount of labor has been spent in making tables of the weather, and of almost every conceivable earthly phenomenon which may be supposed to have a similar periodic character, with very doubtful success, nearly every one having brought out some result which might be plausible if it stood alone, but which is apt to be contradicted by the others. For instance, Mr. Stone, at the Cape of Good Hope, and Dr. Gould, in South America, consider that the observations taken at those places show a little diminution of the earth’s temperature (amounting to one or two degrees) at a sun-spot maximum. Mr. Chambers concludes, from twenty-eight years’ observations, that the hottest are those of most sun-spots. So each of these contradicts the other. Then we have Gelinck, who, from a study of numerous observations, concludes that all are wrong together, and that there is really no change in either way.

I might go on citing names with no better result. One observer tabulates observations of terrestrial temperature, or rain-fall, or barometer, or ozone; another, the visitations of Asiatic cholera; while still another (the late Professor Jevons) tabulates commercial crises with the serious attempt to find a connection between the sun-spots and business panics. Of making such cycles there is no end, and much study of them would be a weariness I will not inflict.

Our own conclusion is, that from such investigations of terrestrial changes nothing is yet certainly known with regard to the influence of sun-spots on the weather. There is, however, quite another way; that is, to measure their effect at the origin in the sun itself. The sun-spot is cooler than the rest of the surface, and it might be thought that when there are many the sun would give less heat. As far as the spots themselves are concerned, this is so, but in a very small degree. I have been able to ascertain how much this deprivation of heat amounts to, and find it is a real but a most insignificant quantity, rising to about two-thirds of one degree Fahrenheit every eleven years. This, it will be remembered, is the direct effect of the spots considered merely as so many cool patches on the surface, and it does not imply that when there are most spots the sun will necessarily give less heat. In fact there may be a compensating action accompanying them which makes the radiation greater than when they are absent. I will not enter on a detailed explanation, but only say that in the best judgment I can form by a good deal of study and direct experiment, there is no certain evidence that the sun is hotter at one time than at another.

If we investigate, however, the connection between spots and terrestrial magnetic disturbances, we shall find altogether more satisfactory testimony. This evidence is of all degrees of strength, from probability up to what may be called certainty, and it is always obtained, not by a priori reasoning, but by the comparison of independent observations of something which has happened on the sun and on the earth. We will first take an instance of what we consider the weakest degree of evidence (weak, that is, when any such single case is considered), and we do so by simply quoting textually three records which were made at nearly the same time in different parts of the world in 1882.

A certain spot had been visible on the sun at intervals for some weeks; but when on the 16th of November a glimpse was caught of it after previous days of cloudy weather, the observer, it will be seen, is struck by the great activity going on in it, and, though familiar with such sights, describes this one as “magnificent.”

1. From the daily record at the Allegheny Observatory, November 16, 1882:—

At the same time a sketch was commenced which was interrupted by the cloudy weather of this and following days. The outline of the main spot only is here given (Fig. 49). Its area, as measured at Allegheny, was 2,200,000,000 square miles; at Greenwich its area, inclusive of some outlying portions, was estimated on the same day to be 2,600,000,000 square miles. The earth is shown of its relative size upon it, to give a proper idea of the scale.

2. From the “New York Tribune” of November 18th (describing what took place in the night preceding the 17th):—

And so on through a column.

3. In Fig. 50 we give a portion of the automatic trace of the magnetic needles at Greenwich.3 These needles are mounted on massive piers in the cellars of the observatory, far removed from every visible source of disturbance, and each carries a small mirror, whence a spot of light is reflected upon a strip of photographic paper, kept continually rolling before it by clock-work. If the needle is still, the moving strip of paper will have a straight line on it, traced by the point of light, which is in this case motionless. If the needle swings to the right or left, the light-spot vibrates with it, and the line it traces becomes sinuous, or more and more sharply zigzagged as the needle shivers under the unknown forces which control it.

The upper part of Fig. 50 gives a little portion of this automatic trace on November 16th before the disturbance began, to show the ordinary daily record, which should be compared with the violent perturbation occurring simultaneously with the telegraphic disturbance in the United States. We may, for the reader’s convenience, remark that as the astronomical day begins twelve hours later than the civil day, the approximate Washington mean times, corresponding to the Greenwich hours after twelve, are found by adding one to the days and subtracting seventeen from the hours. Thus “November 16th, twenty-two hours” corresponds in the eastern United States nearly to five o’clock in the morning of November 17th.

The Allegheny observer, it will be remembered, in his glimpse of the spot on November 16th, was struck with the great activity of the internal motions then going on in it. The Astronomer Royal states that a portion of the spot became detached on November 17th or 18th, and that several small spots which broke out in the immediate neighborhood were seen for the first time on the photographs taken November 17th, twenty-two hours.

“Are we to conclude from this,” it may be asked, “that what went on in the sun was the cause of the trouble on the telegraph wires?” I think we are not at all entitled to conclude so from this instance alone; but though in one such case, taken by itself, there is nothing conclusive, yet when such a degree of coincidence occurs again and again, the habitual observer of solar phenomena learns to look with some confidence for evidence of electrical disturbance here following certain kinds of disturbance there, and the weight of this part of the evidence is not to be sought so much in the strength of a single case, as in the multitude of such coincidences.

We have, however, not only the means of comparing sun-spot years with years of terrestrial electric disturbance, but individual instances, particular minutes of sun-spot changes, with particular minutes of terrestrial change; and both comparisons are of the most convincing character.

First, let us observe that the compass needle, in its regular and ordinary behavior, does not point constantly in any one direction through the day, but moves a very little one way in the morning, and back in the afternoon. This same movement, which can be noticed even in a good surveyor’s compass, is called the “diurnal oscillation,” and has long been known. It has been known, too, that its amount altered from one year to another; but since Schwabe’s observations it has been found that the changes in this variation and in the number of the spots went on together. The coincidences which we failed to note in the comparison of the spots with the prices of grain are here made out with convincing clearness, as the reader will see by a simple inspection of this chart (Fig. 51, taken from Professor Young’s work), where the horizontal divisions still denote years, and the height of the continuous curve the relative number of spots, while the height of the dotted curve is the amount of the magnetic variation. Though we have given but a part of the curve, the presumption from the agreement in the forty years alone would be a strong one that the two effects, apparently so widely remote in their nature, are really due to a common cause.

Here we have compared years with years; let us next compare minutes with minutes. Thus, to cite (from Mr. Proctor’s work) a well-known instance: On Sept. 1, 1869, at eighteen minutes past eleven, Mr. Carrington, an experienced solar observer, suddenly saw in the sun something brighter than the sun,—two patches of light, breaking out so instantly and so intensely that his first thought was that daylight was entering through a hole in the darkening screen he used. It was immediately, however, made certain that something unusual was occurring in the sun itself, across which the brilliant spots were moving, travelling thirty-five thousand miles in five minutes, at the end of which time (at twenty-three minutes past eleven) they disappeared from sight. By good fortune, another observer a few miles distant saw and independently described the same phenomenon; and as the minute had been noted, it was immediately afterward found that recording instruments registered a magnetic disturbance at the same time,—“at the very moment,” says Dr. Stewart, the director of the observatory at Kew.

“By degrees,” says Sir John Herschel, “accounts began to pour in of ... great electro-magnetic disturbances in every part of the world.... At Washington and Philadelphia, in America, the telegraphic signal men received severe electric shocks. At Boston, in North America, a flame of fire followed the pen of Bain’s electric telegraph.” (Such electric disturbances, it may be mentioned, are called “electric storms,” though when they occur the weather may be perfectly serene to the eye. They are shown also by rapid vibrations of the magnetic needle, like those we have illustrated.)

On Aug. 3, 1872, Professor Young, who was observing at Sherman in the Rocky Mountains, saw three notable paroxysms in the sun’s chromosphere, jets of luminous matter of intense brilliance being projected at 8h. 45m., 10h. 30m., and 11h. 50m. of the local time. “At dinner,” he says, “the photographer of the party, who was making our magnetic observations, told me, before knowing anything about what I had been observing, that he had been obliged to give up work, his magnet having swung clear off the limb.” Similar phenomena were observed August 5th. Professor Young wrote to England, and received from Greenwich and Stonyhurst copies of the automatic record, which he gives, and which we give in Fig. 52. After allowing for difference of longitude, the reader who will take the pains to compare them may see for himself that both show a jump of the needles in the cellars at Greenwich at the same minute in each of the four cases of outburst in the Rocky Mountains.

While we admit that the evidence in any single case is rarely so conclusive as in these; while we agree that the spot is not so much the cause of the change as the index of some other solar action which does cause it; and while we fully concede our present ignorance of the nature of this cause,—we cannot refuse to accept the cumulative evidence, of which a little has been submitted.

It is only in rare cases that we can feel quite sure; and yet, in regard even to one of the more common and less conclusive ones, we may at least feel warranted in saying that if the reader forfeited a business engagement or missed an invitation to dinner through the failure of the telegraph or telephone on such an occasion as that of the 17th of November, 1882, the far-off sun-spot was not improbably connected with the cause.

Probably we should all like to hear some at least equally positive conclusion about the weather also, and to learn that there was a likelihood of our being able to predict it for the next year, as the Signal Service now does for the next day; but there is at present no such likelihood. The study of the possible connection between sun-spots and the weather is, nevertheless, one that will always have great interest to many; for even if we set its scientific aim aside and consider it in its purely utilitarian aspect, it is evident that the knowledge how to predict whether coming harvests would be good or bad, would enable us to do for the whole world what Joseph’s prophetic vision of the seven good and seven barren years did for the land of Egypt, and confer a greater power on its discoverer than any sovereign now possesses. There is something to be said, then, for the cyclists; for if their zeal does sometimes outrun knowledge, their object is a worthy one, and their aims such as we can sympathize with, and of which none of us can say that there is any inherent impossibility in them, or that they may not conceivably yet lead to something. Let us not, then, treat the inquirer who tries to connect panics on ‘Change with sun-spots as a mere lunatic; for there is this amount of reason in his theory, that the panics, together with the general state of business, are connected in some obscure way with the good or bad harvests, and these again in some still obscurer way with changes in our sun.

We may leave, then, this vision of forecasting the harvests and the markets of the world from a study of the sun, as one of the fair dreams for the future of our science. Perhaps the dream will one day be realized. Who knows?