CHAPTER II.

SOLI-LUNAR DOMINION IN THE ORGANIC WORLD.

EFFECTS OF LIGHT AND HEAT ON THE DEVELOPMENT AND DISTRIBUTION OF PLANTS AND ANIMALS AND OF THE HU

MAN

RACE.-DIURNAL AND SEASONAL CHANGES IN RELA

TION TO HEALTH AND DISEASE.

WE have

E have traced the supreme and all-pervading influence which the "two great lights" appointed to rule the day and night exert, in the production of inorganic terrestrial change. It remains to observe their effect on organized existences, on plants and animals, and on man himself. In this wide and interesting realm, as in the previous one, we shall find that solar influence is supreme.

Light and heat are the most powerful of all agents in the quickening and support of animal and vegetable life, and of these the sun is of course the great source and centre. By its presence or absence, are caused our day and night; and by its elevation or depression, our seasons. These, in their varied alternations, set in motion and control the entire world of organized existence.

What simplicity and sublimity in these solar revolutions and their results! The dawning of day is the signal for the world's awaking from that deathlike sleep which is the child of darkness; with the rising of the sun the flowers open, the birds burst forth into song, and everywhere is seen the stirring of life and activity. The duration of the day sustains and nourishes the infinitely numerous and complicated organic movements and revolutions it has awakened, and its termination reproduces universal silence and repose.

Were the days considerably to lengthen or shorten, were the seasons to change or cease, how immense and disastrous would

be the results to all organized existences! The permanence of seed-time and harvest, day and night, cold and heat, has been promised by the sure word of a gracious and bountiful Creator, and the accomplishment of that promise is effected by the permanence and stability of the earth's actual relations with the sun. These may slightly vary in the course of the prolonged secular changes, discovered by astronomic observation, but compensating powers exist which keep these changes within very narrow limits, and provide for the maintenance of equilibrium, thus securing that uniformity of solar influence, which is needful for the continuation of terrestrial life.

The inclination of the axis of the earth, to the plane of her orbit, for instance, is at present undergoing a steady, though very slow diminution. Were this to continue, unchecked, or to accelerate, a time must come sooner or later, when the equator and the ecliptic would coincide, and thus destroy the present succession of the seasons.

But this catastrophe will never happen; the all-wise Creator has provided for a continuance of the works of his hands. Before the movement of the earth's axis in this direction can produce any perceptible results, in changing the climate of any part of the globe, it will cease. The axis will, under fresh influences, remain steady for a time, and then commence a retrograde movement, which will restore it to its original position. It will thus oscillate to and fro in the ages to come, without ever deranging to the slightest extent, the climate of the various parts of the earth.

The extent of solar influence in the organic world, is marvellous to contemplate. The sun is the glowing ever acting heart of organic nature; the succession of day and night are the pulsation, the systole and diastole, the contraction and expansion of that heart. The sun is the all-important reservoir of life-supporting power, constantly sending its royal tide of vitalizing light and heat, through all the arteries of the mundane system, to its uttermost extremities, penetrating its utmost recesses and lowest depths, with its life-giving warmth.

Vegetable life, without exception, is generated under the sun's quickening influence; without it, not a seed would germinate, not a blade would spring, not a leaf would shoot, not a bud would burst, not a petal would unfold, not a flower would bloom, not a fruit would ripen. It alone raises and distils the dews and rains which feed and nourish the entire world of plants; it alone dyes the field and the forest with their verdure; it alone paints the blossom with its beauty, and tints with hues of loveliness both earth and heaven. It gives birth to the breezes, which stir the movements of every leaf and branch, scatter seeds and perfumes, and strip away all that has withered or yielded to decay. It is the joyful parent of spring, and the fruitful fount of summer wealth and autumnal glory.

Animals are equally indebted to the sun. Without it none of the innumerable forms of animal life could for a moment exist. Without its warmth all muscular power would be paralysed, the frozen blood would fail to circulate, respiration would cease, and life would inevitably become extinct. Its rising and its setting, its shining and withdrawing, its ascent in summer, its decline in autumn and winter, and return in spring, control the cycles and create the boundaries, of all the phases of animated nature, the sleeping and the waking, the stillness and the activity, the silence and the song, the action, the passion, and the repose of innumerable tribes of living creatures, peopling air and earth and seas.

Man walks in its light, labours in its heat, basks in its smile, rejoices in its glory. It is the constant and irresistible ruler of days, and years, and seasons, and is enthroned as such, from generation to generation, and from age to age. In all these respects, it is the most glorious and sublime of all the material emblems of HIM, from whose creative fiat, it of old derived existence and dominion, and by whose unfailing power it is upheld; of Him who is the blessed and only Potentate, the King of kings and Lord of lords, the eternal and overflowing Source of light and love.

As the moon only reflects the sun's light in a very modified

degree, and no perceptible portion of its heat, it exercises little direct influence on organized nature. Its indirect action upon the organized forms contained in, or affected by, the many seas, estuaries, and tidal rivers of the world, is very considerable. The existence of the immense variety of plants and animals which live on the shores or boundaries of sea and land, is to a large extent conditioned by the ebb and flow of tides. To man, the moon is a useful and beautiful night lamp, and an invaluable chronometer, while by its daily, world wide, tidal movement, it is as we have seen, next to the sun, his most powerful natural aid. It rules for him the night, and regulates his calendar, indicating by its movements, in conjunction with the sun, the measures of time which he universally adopts and follows.

A few familiar facts, illustrative of the above statements, may serve to give them the weight they deserve, and if any apology be needful for recalling natural phenomena, with the existence of which many if not most are familiar, it must be found in the necessity which we are under, of firmly establishing the great truth of soli-lunar dominion over terrestrial movement and change, in order to the due appreciation of the subsequent portion of this treatise.

Be it then remembered that the sun not only produces day and night, and the succession of seasons in each particular locality, regulating by this means, the growth and activity of organized nature, but by its various degrees of elevation in different latitudes, it causes all the varieties of climates, and through these, the development and distribution of vegetable and animal life throughout the world. These various degrees of elevation, causing the sun to afford varying degrees of light and heat, produce the different zones into which our globe, as regards climate, is divided. The principal zones are the equatorial zone, the tropical zones, the subtropical, the warmer temperate, the colder temperate, the sub-arctic, the arctic, and the polar zones.

Now life, whatever may be its origin, clearly depends for its

continuance, on the physical conditions by which it is surrounded. According to the degrees of moisture or drought, heat or cold, the plant or animal flourishes, or languishes and dies. It is only in the case of certain plants and animals, that "acclimatization" under non-natural circumstances is possible, and even with these, it is possible only within certain limits, and by the greatest care. The flora peculiar to a region of excessive drought, will not survive removal to a region of excessive humidity, nor will ferns and marsh plants thrive in the desert. It is obvious, therefore, that on a globe where the sun produces such diversity of climate, life must exist under widely diversified forms. No region, save the extreme polar perhaps, is utterly destitute of it, but each has its own peculiar development. The intertropical regions of the earth, having in greatest perfection the conditions favourable to life, or in other words having a large share of solar heat and light, have an exuberant growth of vegetable life and a redundance of animal existence. This decreases in each zone as we proceed towards the poles, till we reach the boundary, where a minimum of solar light and heat forbid the existence of any form of life.

Since temperature similarly decreases, as we ascend from the level of the sea into the higher regions of the atmosphere, vegetation varies, not only according to latitude, but according to altitude. The Alpine traveller may pass through the climates. of the various zones in one day. He leaves the rich vineyards, and the flowering myrtle and pomegranate, the fruit-bearing orange and lemon-trees behind him, in the valley; passes through woods of oaks, sweet-chestnuts and beeches, as he mounts the lower slopes; and amid pines and birches, as he gains the higher parts of the mountain, till at last he finds only the short fine occasional pasture grass, and subsequently nothing but lichens and mosses, edging the beds of perpetual snow and ice. The vine disappears before he has climbed two thousand feet; the chestnuts have vanished at three; the oak fails to put in an appearance at four, and the birch long before he has climbed five thousand feet. The spruce-fir greets him as