Popular Science Monthly/Volume 54/December 1898/The Season of the Year
|THE SEASON OF THE YEAR.|
A YEAR is, roughly speaking, the period which it takes the earth to perform one complete revolution round the sun. I say "roughly speaking" with due humility, having the fear of the expert ever before my eyes, because I know that if I do not sing small, that inconvenient person, the astronomical critic, will come down upon me at once like a wolf on the fold, with minute distinctions about the mean, the tropical, and the sidereal year; matters of immense importance at Greenwich Observatory, no doubt, but elsewhere of very little interest indeed, seeing that they differ from one another by so many minutes only. Let us leave the astronomers their own problems. The year with which I am going to deal humbly here is a much more commonplace, ordinary, and comprehensible year—the visible year of vegetation, of plant and animal life, of the four seasons; the year as roughly known to children and savages, and to the weeds, the flowers, the bees, and the squirrels.
It has often struck me as curious that people took this complex concept of the year so much for granted-—inquired so little into its origin and discovery. Yet it is by no means everywhere obvious. How did men first come to notice, in the tropics especially, that there was such a thing as the year at all? How did they first observe, save in our frozen north, any fixed sequence or order in the succession of Nature? How did they learn, even here, that spring would infallibly follow winter, and summer be succeeded in due course by autumn? And, to go a step farther back, how did the plants and animals, in all parts of the world alike, come originally to discover and adapt themselves to all these things? How did the bee know that she must "gather honey all the day from every opening flower," the summer through, in order to use it up as bodily fuel in winter? How did the plants learn when to blossom and produce seed? In one word, how did the seasons come to be automatically recognized?
That they are automatically recognized, even by plants, quite apart from the stimulus of heat or cold, drought or rain, a single fact (out of many like it) will sufficiently prove. Trees brought from Australia to England, where the seasons are reversed, try for two or three years to put forth leaves and flowers in October or November—the southern spring. It takes them several autumns before they learn that the year has been turned upside down—that June is now summer and December winter. This shows that life moves in regular cycles, adapted to the seasons, but not directly dependent upon them. The rhythm of the world has set up an organic rhythm which now spontaneously and automatically follows it.
At first sight, to the dweller in the temperate zone at the present day, the questions I have put above may seem needless, not to say childish. But that is perhaps because we have all too much the habit of taking it for granted that what is true here and now has also been true everywhere and always. A first visit to the tropics often enough rudely disturbs this uninquiring attitude of mind. For in the tropics, and especially in the equatorial region, there is no winter and no summer, no spring and no autumn. The world wags wearily through an unending display of monotonous greenery. As far as temperature goes, the year is pretty much alike in all its months. Yet not only do equatorial men recognize the existence of the year as a natural epoch quite as much as other men—not only do equatorial savages celebrate annual feasts, count ages by years, and perform certain rites in certain months only—but also animal and vegetable nature recognizes the year; trees have their month for blossoming and fruiting, birds their month for assuming the plumage of courtship, for nesting and hatching, almost as markedly as elsewhere. The recognition of the year both by man and by Nature is not therefore entirely dependent upon the difference of summer and winter, as such. We must go deeper, and I think, when we come to consider geological time, much deeper, if we wish to understand the true character of yearliness—a word which I venture here to coin to express this meaning.
Have you ever quite realized what the tropical year is like? Suppose you are living on or near the equator, then in December the sun is south of you and at its greatest distance away; you have, so to speak, a relative winter. But in March the sun is overhead; it is now full midsummer. By the end of June the sun has gone north, and is once more on a tropic; you have a second winter; not much of a winter, I admit, but still, a relative winter. By September he has returned overhead again, and you are enduring a second summer. In December he has once more retreated to the southern tropic (Capricorn), and it is comparative winter. Thus the equatorial year consists of four distinct seasons, in two of which the sun stands directly overhead, while in two he is at his northern or southern limit. I may add that the effect is always curious when, as you face the sun, you see that he is moving in his diurnal path, not from left to right ("the way of the sun," as we say), but from right to left (or "widdershins"). You are never till then aware how natural and inevitable has seemed the opposite direction: when you find it reversed the effect is surprising.
Now, the distance to which the sun travels north or south of you, if you live on the equator—I use ordinary terms instead of astronomical ones for simplicity's sake—-is so comparatively small that within the tropics themselves you never notice much difference as to the amount of heat between one period of the year and another. In equatorial countries the day and night temperature is much the same all the year round: if the country be plain, it is always hot; if mountainous, like the district about Bogotá, it is "a perpetual spring"; one day is always much the same as the one that went before and the one that comes after it. Even on the actual tropics, again, the difference is too slight to make any marked change in the temperature; people living on the northern tropic (Cancer), for example, have the sun vertical to them on June 21st, and some forty-three degrees south of them on December 21st. Nevertheless, the sun is still as near them and as powerful as he is at Milan or Venice in the height of summer; and the consequence is that, as a matter of fact, the thermometer within the tropics and at sea level seldom descends below 75° or 80°, even at midnight in the relative winters. For the heating power of the sun depends, of course, upon the directness of his rays, and lessens with their obliquity; in Venice and Milan they are strong enough to make the ground very hot in July and August, though it has been cooled before by a northern winter; much more than in Jamaica or Madagascar, which have never been cooled, does the accumulated heat keep everything warm even when the sun is most oblique—and he never reaches the same obliquity as in an English summer. The ground is hot, the houses are hot, wood and stone are hot, and they have all been hot from time immemorial.
Yet tropical and equatorial trees and plants have their definite seasons to flower and fruit, just the same as elsewhere. This seems surprising at first when one visits the tropics. You can not see why everything should not flower and fruit the whole year round. And yet, at one time pineapples are "in," at another mangoes. And these seasons differ in the northern and southern hemispheres; what is mango winter in the one being mango summer in the other. I do not say the seasons anywhere in the tropics differ markedly; still, they do differ; the tropical year is divided into times and months for agriculture just as much as any other. Thus there are regular dates in each hemisphere for planting, tending, and cutting the sugar cane. Now, what is the reason of these changes in vegetation, when temperature remains so constant? Why do not trees and shrubs of each kind flower up and down throughout the year irregularly—now one individual and now another? Why are there seasons for things at all in the tropics?
The answer is, because the same causes which produce summer and winter in temperate climate produce other changes of other sorts in the tropical region. The temperature, it is true, remains the same, or approximately the same; but the meteorological conditions vary. Even with ourselves, summer is not only hotter but also drier than winter; winter is marked by rain and snow as well as by lowered temperature. In the tropics, on the other hand, it is rather the summer or summers that are wet, for there is a certain moving zone of equatorial calms in which it practically keeps on raining always. But this zone is not fixed; it flits with the sun. When the sun goes northward for the northern summer the rainy zone goes with him; when he turns southward again the zone shifts after him. Thus places on or near the two tropics have one rainy season a year, while places on the equator have usually two. The intervening dry seasons are often very dry and parched, indeed; and where this is markedly the case, the rainy season acts just as spring does in the north, or as the inundation does in Egypt; it is the beginning of vegetation. The plants that were dry and dormant during the arid months wake up into fresh life; the branches put forth new leaves; the brown seeds germinate; the flowers appear; and in due time the fruit ripens. Everything in these cases depends upon the recurrence of the rainy season, just as everything in India depends upon the bursting of the monsoons, and everything in Egypt on the rising of the Nile. I have seen a dry plain in Jamaica bare and brown one day, and covered six or eight inches high with fresh green waving guinea-grass the day but one after. The rains had came meanwhile, and Nature had awaked with more than springlike awakening. In those hot climates everything grows by magic as soon as it gets the needed water.
Indeed, we may say that in half the world the seasons, organically speaking—I mean, the seasons of plant and animal life—depend upon heat and cold, summer and winter, snow or sunshine; but in the other half they depend almost entirely upon drought and rainfall. Even as near home and as far north as Algeria, the summer is far too dry and dusty for agriculture; the autumn rains set in about October or November; they are immediately followed by the plowing; and the winter becomes for most purposes the practical summer. Fruits and vegetables are at their best in January and February; the fields are full of flowers up to March or April; in June, July, and August the country is an arid and weary desert. But the seasons for dates are almost reversed; they ripen in autumn. In Egypt again, where everything depends upon the inundation, the seasons are still more complicated; the inundation begins to subside in October; in Upper Egypt the winter season which follows is far the most important for agriculture, and crops sown as the water subsides are reaped from four to seven months after. But in the Delta, rice, cotton, and indigo are sown in the spring (March or April) and harvested in October, [November, and December. Here, irrigation and temperature come in as disturbing elements, for the Delta feels something of the cold of winter.
I could give many other instances, but these will suffice. As a general rule, we may say that in the temperate and frigid zones the seasons for plants and animals are ruled by heat and cold, but that in tropical and even in subtropical climates, rainfall and drought, themselves largely due to the same circumstances, are the ruling factors.
Again, everybody knows that winter and summer, and the other phenomena which simulate or accompany them, such as wet and dry seasons, depend upon the fact that the earth's axis is not perpendicular to the plane in which the earth moves round the sun, but slightly inclined to it. Now, a year in itself, viewed as a measure of time, is merely the period which it takes the earth to perform one such complete revolution. During one half of each such revolution the north pole is turned at a considerable angle toward the sun, and during the other half, the south pole. When the north pole is so turned we call it summer in the northern hemisphere; when the south pole is being favored, and the north is receiving less light and heat, we call it winter. Let us suppose for a moment that the earth had not got this twist or kink in its axis; that the equator was always presented exactly toward the sun; what then would happen? Obviously, there would be no change of seasons. The day and night would have fixed lengths which never varied; climate would in each place be uniform and, barring accidents of elevation or distribution of land and water, the climate of each place would also depend entirely the whole year round on its distance from the equator. Roughly speaking, the temperature of a district would be the temperature it now possesses in March and September, only not quite so cold as March nor so warm as September, owing to the absence of accumulated heat from summer or of reserves of ice and snow from winter. In one word, under such conditions there would have been climates—marked belts of climate; but there would not have been seasons.
Seasons, however, depend in great part, as Mr. Alfred Russel Wallace has ingeniously shown, on a great many things besides this mere inclination of one end or the other of the earth toward the sun in June and January. Much must be laid to the count of accumulated stores of heat or cold; and though accumulated cold is physically a misnomer, still for all practical purposes we may apply the words fairly enough to the ice caps of the pole and the glaciers of mountain systems. And here we come face to face with the very core of our problem: for the odd part of it is that seasons (at least as we know them) seem to be quite a recent and exceptional phenomenon in the history of our planet. So far as we can judge, geologically speaking, the earth during all its earlier life enjoyed, over all its surface, what we should now consider tropical or subtropical conditions. England—or rather the land that occupied the part of the earth's crust where England now stands—had a vegetation of huge tree ferns and palms and cycads during the Primary period; as late even as the middle Tertiaries it had a vegetation like that of South Carolina or Upper India. Greenland itself, in quite recent times, nourished like a green bay tree, and did not belie its odd modern name. The world as a whole enjoyed perpetual summer: In one word, except in something like the equatorial sense, there were practically no seasons. The sun went north and south, no doubt, as now, but the temperature, even in the relative winter, seems to have remained perennially mild and genial.
It is true, occasional slight traces of glacial epochs, earlier than the great and well-known Glacial epoch, break here and there the almost continuous geological record of palmy and balmy world-wide summers; yet, taking the geological monuments as a whole, they show us few or no signs of anything worth calling a serious winter till quite recent periods. Large-leaved evergreens are still, in the day-bef ore-yesterday of geology, the order of the day; magnolias and liquidambars, cinnamons and holly oaks, vines and rotang palms formed the forests even of Miocene Britain. The animals during all the Tertiary period were of what we now regard as tropical or subtropical types—lions, rhinoceroses, hippopotamuses, monkeys, or more antique races, equally southern in aspect. There could have been little change of winter and summer during this long warm spell; the variations can have been scarcely more than those of dry and rainy seasons. The trees never lost their leaves; the fruits and flowers never ceased to follow one another; no interruption of the food supply drove insects to hibernate in their silken cocoons, or squirrels and bears to lay by stores of food or fat for the cold and hungry winter.
Nevertheless, taking the world round as it stands, we must believe that the distinction of seasons grew up, both for plants and animals, and for man or his ancestors, during this age of relatively unmarked summers and winters. For the tropics more than anywhere else preserve for us to-day the general features and aspect of this earlier time; they have never had the continuity of their stream of life rudely interrupted by the enormous changes of the Glacial epoch. Yet, even in the tropics, things, as we saw, have seasons. There are annuals and perennials there, as elsewhere. Each kind has its month for sprouting, for flowering, for fruiting, for shedding its seed; and men in the tropics, some of them long isolated in oceanic islands, or in great insulated regions like Australia or New Guinea, from the rest of their kind in the temperate regions, nevertheless know and observe the year, and perform all their functions, agricultural or religious, by yearly cycles. For example, there is among them all an annual feast for the dead, and widows mourn their husbands for one year from their burial. Observation of the year, therefore, both automatically by organisms at large and consciously by man, antedates and is independent of observation of the existence of summer or winter.
I do not think, however, that man would have noted the merely astronomical year—the year of the sun's position—at least till a relatively late stage in culture, if he had not first noticed the organic year—the regular recurrence of plant and animal seasons. So many yams—that is to say, so many yam harvests—in other words, so many years, is a common savage way of reckoning times and ages. But they call it "yams," not summers or winters. And when I say yams, I give that merely as a single instance, for elsewhere the "seedtime and harvest" are reckoned indifferently in maize or millet, rice or barley, according to the agriculture of the particular people. Even hunting races know that at certain times of year certain foods abound; and this is true of equatorial savages and equatorial plants or animals, as well as of others.
Moons are more obvious measures of time than suns, in the tropics at least—probably everywhere; for the waxing and waning of the moon mean much to people who live largely out of doors; and the month is, perhaps, the earliest fixed mode of reckoning time beyond a day or two. Most savages count time mainly by so many moons. But they must also have noticed early that after a certain number of moons (usually about thirteen), certain fruits or seeds were ripe again; especially must they have noticed it when this recurrence coincided with the return of the rainy season, or of some other annual meteorological phenomenon, like the bursting of the monsoon or the Nile inundation. Thus, even in the tropics, and before the coming on of the Glacial epoch, men or the ancestors of men (one can not draw precise lines here) must probably have observed a certain rough relation between the months and the vegetative cycles; after so many moons, about say thirteen, the yam, or the mangoes, or the grains are ripe again. These organic years, I take it, must have been noticed before the astronomical ones. For it is now beginning; to be more and more believed that man is of preglacial origin; and even if something worth calling a man were not, then at least man's pre-human ancestors go back far into the Tertiary period. Only later would men begin to note that some thirteen moons, and the recurrence of a food stuff, concurred with a particular solar season.
Indeed, if one comes to think of it, how much even now do any of us, save the most scientific, mean by the year, beyond the visible change of summer and winter? What we are thinking of is the leafless trees, the ice and snow, the green grass in spring, the flowers and warm days in summer, not the abstract astronomical fact of the earth's revolution round the sun, or the due succession of the signs of the zodiac. It is that visible organic year that must have counted most with man from the first; though no doubt its meaning and reality are much more vividly present since the coming on of the Glacial epoch, and the more so in proportion as we live nearer to the north or south pole; while at the equator the year is to the last a much more inconspicuous period—a largely artificial mode of reckoning.
Still, from the very first, there was one element of diversity in the year which must have struck all men, in the temperate and frigid zones at least, perhaps even in a certain way in the tropics. I mean, the varying length of the day, always perceptible in the frigid and temperate zones; for as soon as men in these regions began to think and to observe at all, they must have noticed that the days increased in their summer and lessened in their winter; and they must have learned to correlate this waxing and waning of the day with the appearance or abundance of certain fruits, seeds, birds, fishes, game, roots and other food stuffs. It is at least certain that all the world over men do now celebrate the solstices and the equinoxes as special feasts; and the close similarity in most such celebrations leads one to suspect that the custom has been handed down from the very remote time when the human family was still a single continuous body.
In the tropics, it is true, the days vary so little that this difference in itself is not likely to have struck primæval man. But there, another point would come in—the annual movement of the sun overhead from south to north and vice versa; and though this would be less directly important to human life than in temperate regions, it would still be indirectly important. It would bring the rain with it. In Europe, of course, and in temperate America, we can see at once that the return of the sun northward must always have meant spring, the increase of food stuffs, the promise of corn or maize, the suggestion of harvest; and we can therefore understand why the midwinter feast, when the sun after his long journey south begins to move visibly north again, should have been both in pagan and Christian times the great festival of rejoicing for the men of the north temperate region. Day by day they saw the sun recede and the cold deepen; at last, one evening, he sets a little nearer, and they know that he has not deserted them forever. Similarly, the promise made at Yule begins to be realized at that other great feast of the spring equinox, which we still call in England by its ancient heathen title of Easter; the day by that time has got the better of the night, and "the sun dances on Easter Sunday" in commemoration of his completed victory over the combined powers of winter and darkness. In the tropics, on the other hand, the connection is less clear; but even here the shifting of the sun's apparent place is closely correlated with the shifting of the rain zone; and therefore it would not be long (after man was man) before tropical savages began to perceive a constant relation between the movements of the sun to north or south, and the occurrence of the fertilizing rainy season. We must remember that savages, with their improvident habits, are much more dependent upon rain than we are, and that magical ceremonies for breaking up a drought are among their commonest and most universally diffused superstitions.
On the whole, then, before the coming on of the Glacial epoch, we may be pretty sure that plants and animals on the one hand had learned organically and automatically to recognize the existence of the year and to adapt themselves to it; and that men or the progenitors of men on the other hand had also learned to correlate the recurrent seasons of food supply with the movements of the sun, though nothing equivalent to winter and summer as we know them to-day existed as yet on any part of our planet. I say advisedly "on any part of our planet," because even near the pole itself remains of a subtropical vegetation in Tertiary times have been amply indicated. Nevertheless, in all parts of the world then, as in the tropics now, we may gather that plants and animals ran through annual cycles—that the year, as I have put it, was organically recognized. Trees had their time to sprout, to bud, to flower, to fruit, to seed, to shed their leaves (in the evergreen way); birds had their time to nest and hatch out their young; insects had their fixed periods for laying, for larval life, for assuming the chrysalis form, for becoming winged beetles or bees or butterflies. In one word, the year is a terrestrial reality, not merely an astronomical fact, in the tropics now; it was a terrestrial reality over the whole planet in the Tertiary period. But it was hardly more marked, apparently, into distinct seasons than it is marked to-day in the equatorial region. Rainfall and drought must have had more to do in determining the annual cycles than winter and summer.
From all this it must result that the conception of the year as an epoch at all (save for advanced astronomy) is almost or entirely due to that tilt of the earth's axis which causes the seasons—dry or wet, cold or hot. Without the seasons, in one form or other, we might have been ages longer in discovering the fact that the earth moved round the sun, and that some three hundred and sixty-five days (I omit those important fractions) were needed for its revolution. Certainly, without the seasons, at least to the extent that they occur in the tropics, plant and animal life could hardly have assumed its fixed annual cycles, nor could early men have caught at the idea of the year at all as a period of time, a unit of measurement.
Before the Glacial epoch, in particular, the discovery of the year, organically or consciously, must have been much more difficult than it is now in high latitudes. It must have been almost as difficult in what are now the temperate zones as it is to-day in the tropics. Far north or south, of course, the length of the day would tell; and within the Arctic and Antarctic Circles the long night would form an unmistakable feature. But if the plane of the equator had always found itself vertical to the sun, there could have been no recognition of the year at all, either organic or conscious. In other words, from the point of view of organic life, the year does not mean the revolution of the earth round the sun: it means the apparent northward and southward movement of the sun on either side of the equator; it means the seasons, whether recognized as winter and summer, or as dry and wet periods. That is really the year as man knows it, as plants and animals have always known it.
With the coming on of the great cold spell, however, the importance of the seasons in the temperate and frigid zones, perhaps also even in the tropics, became much more marked. I will not go here into the suggested reasons for that vast revolution, perhaps the greatest our planet has ever suffered. Most physicists now accept more or less the theory put forward with great ingenuity by Mr. Croll, which sets it down to a period of extreme eccentricity in the earth's orbit; but some weight must also be allowed, as Mr. Alfred Russel Wallace has clearly shown, to the local arrangement of land and water on the globe at the time of its origin, as well as to the occurrence of mountain ranges just then at the poles, and to other purely terrestrial causes. Never before, in all probability, had the poles been occupied by great glacier-clad mountains. It seems most likely, indeed, that we are now practically at the end of the Glacial epoch, and that if only we could once get rid of the polar ice caps, which keep a stock of chilliness always laid on (I speak the quite comprehensible language of everyday life), we might recur forthwith to the warm and almost imperceptible winters of the preglacial period. But, as things stand, the stock of ice at the poles never gets melted away in the existing northern or southern summer; fresh ice accumulates on top of the old mass with each winter; prevailing winds, blowing over this ice, chill regions lying much farther toward the tropics; icebergs detach themselves and float off, thus lowering the temperature of the sea in the middle zones; arctic or antarctic currents spread round the coasts and absorb the solar heat in enormous quantities. We have only to remember the trenchant difference in England between a parching cold east wind and a mild sou'wester to realize what an immense part these polar ice caps and frozen highlands play in the production of our existing winter. Alps, Pyrenees, Himalayas, Rocky Mountains, further assist in the same direction.
On the other hand, currents in the sea may cut either way; the Gulf Stream makes England warm, while the arctic current makes Labrador, much farther south, practically uninhabitable.
Ever since the Glacial epoch, therefore, it has been quite easy for man in the temperate and frigid zones to recognize the year as a natural reality. The annual cycles of heat and cold are far too marked to be overlooked by anybody. Organically, they made themselves felt at once by extraordinary changes induced in the fauna and flora. Before the steady advance of the annual cold wave, vegetation had perforce to alter its ways. The large-leaved evergreens went out altogether in frigid and high temperate regions; deciduous trees, or needle-leaved types like the pines and firs, took the place of the luxuriant Miocene foliage in Europe and North America. Every autumn the larger number of trees and shrubs learned to shed their leaves all; every spring they came out anew in fresh green and in masses of blossom. Similarly with animals. Birds learned to migrate, or to accommodate themselves to the winter; insects learned to hibernate in the egg or the cocoon; pigs fattened themselves on mast against the frozen time; moles slept over winter; squirrels hoarded nuts for a store to bridge over heavy frosts; frogs retired to the warmer mud in the depths of ponds; adders coiled themselves in holes and dozed away the cold season. Innumerable adaptations sprang up at once, those species or individuals which failed to meet the new conditions perishing in the struggle. In proportion as we recede from the tropics, the more marked do the annual cycles of life thus induced become, many species practically ceasing to exist as such for several months of the year, and being only potentially represented by eggs, germs, or seeds, and sometimes by dormant pregnant females.
At the same time, while the cause of the seasons as a whole is the obliquity of the earth's axis, with the resulting inclination of either pole toward the sun alternately, we must not forget that the seasons and the climate in each particular country depend in part upon many minor contributory causes. It is not merely nearness to or distance from the equator that counts; we have to consider also relative distribution of land and water, elevation, prevalent winds, exposure, condensation, and many other elements of a complex problem. In Ecuador, for example, whose very name means the equator, the plain is always in scorching summer, the mountains are always in perpetual spring. The monsoons, again, produce in other countries some curious results: they depend themselves on the change of relative temperature in sea and land at different seasons; and they break upon the Himalayas with this odd and unexpected effect, that the snow line on the southern side of that vast range goes very far down, owing to the immense rainfall (or rather snowfall) and the consequent spread of snow fields and glaciers; while on the northern side it descends but a very little way, owing to the extreme desert drought and the great summer heat of the central Asiatic table-land. We have thus the apparent paradox that millions of Tibetans occupy towns and cultivate farms to the north at a height from three to four thousand feet above the snow line on the southern slope of the same mountains.
Looking at the matter broadly, then, and taking for granted the now generally accepted modern view that the great oceans and great continents have been relatively fixed (though liable to minor fluctuations and variations of outline) throughout all geological time, and that the earth's crust has not shifted from pole to equator or vice versa, we arrive at last at the following probable conclusions: There have always been seasons more or less marked, and these have been more or less organically answered by corresponding changes or cycles of change in plants and animals. Rain and drought have in many cases more to do with such changes than variations of temperature. The seasons, again, are less marked in the tropics than in temperate and circumpolar climates. Nevertheless, even near the equator, they exert and have always exerted certain organic influences—have resulted in annual cycles in the life of species. Even before the coming on of the Glacial epoch, the seasons were probably somewhat more marked in the temperate and polar regions than in the tropics, the longer day in summer and the greater directness of impact of the rays making the summer months always warmer. But for various reasons, among which we may presumably rank the absence in early ages of high land at the poles and of an accumulated polar ice cap, together with the existence of warm sea currents from the tropics to the poles, the winters of preglacial ages seem to have been relatively mild, perhaps (if we may judge by the types of plant life) milder than those of South Carolina and Georgia in our own period. No cold winds of importance seem then to have blown with blighting effect from glaciated or snow-clad districts. (Mars in our own time appears to enjoy winters somewhat of this character, though a little colder, with a temporary snow cap.) The seasons as we know them in temperate and arctic climates, however, seem to be largely the result of the glacial epoch, and its persistent legacy the arctic and antarctic ice caps. If we could once manage to get rid of those, it is possible that our planet might again enjoy in all its zones the mild and genial preglacial winters.
These are rough notes, 1 know; mere adumbrations of a probable truth: but adequately to develop the subject would require a very big volume. My object here is simply to suggest that in many inquiries, both into human and animal or vegetable life, we must never take the existence of seasons as we know them for granted, except in very recent times. The year, for organic beings, means essentially the seasons; and the seasons may mean and have meant many separate things, as time and place vary—heat and cold, food and scarcity, foliage and leaflessness, drought and wet; longer or shorter days, the midnight sun and the winter darkness; hibernation and wakefulness; the egg, the cocoon, the seed, the plant, the flower, the fruit; dormancy or vitality. According as human life started at the poles or the equator, for instance, it would view in the beginning many things differently. All I wish to point out now is merely this, that we must bear such possibilities ever in mind; and that we must never take it for granted in any problem, human or biological, that the seasons were always just what we know them, or that the year to any organic being meant anything more than the seasonal cycle then and there prevalent.—Longman's Magazine.
M. A. Thieullen, publishing the results of fifteen years' studies among the flint implements of the French beds, draws the conclusions that the elaborate palæolithic flint axe and hammer and the typical neolithic implements were luxuries used by the more distinguished members or for the more important purposes of the flint-implement-using community, while the ruder implements which are found in enormous numbers were the objects of general and daily use throughout all the flint-using ages, whether palæolithic or neolithic.