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tion to the

tem.

sys

4 Its Application to the Solar System, and Terrestrial Events.

Its applica- thus that, hardly two centuries ago, that doctrine gathered solar immense force from the discovery of Newton that Kepler's laws, under which the movements of the planetary bodies are executed, issue as a mathematical necessity from a very simple material condition, and that the complicated motions of the solar system cannot be other than what they are. Few of those who read in the beautiful geometry of the 'Principia' the demonstration of this fact, saw the imposing philosophical consequences which must inevitably follow this scientific discovery. And now the investigation of the aspect of the skies in past ages, and all predictions of its future, rest essentially upon the principle that no arbitrary volition ever intervenes, the gigantic mechanism moving impassively in virtue of a mathematical law.

And to terrestrial events.

And so upon the earth, the more perfectly we understand the causes of present events, the more plainly are they seen to be the consequences of physical conditions, and therefore the results of law. To allude to one example out of many that might be considered—the winds, how proverbially inconstant, who can tell whence they come or whither they go? If anything bears the fitful character of arbitrary volition, surely it is these. But we deceive ourselves in imagining that atmospheric events are fortuitous. Where shall a line be drawn between that eternal trade-wind, which, originating in well-understood physical causes, sweeps, like the breath of destiny, slowly, and solemnly, and everlastingly over the Pacific Ocean, and the variable gusts into which it degenerates in more northerly and southerly regions,-gusts which seem to come without any cause, and to pass away without leaving any trace? In what latitude is it that the domain of the physical ends, and that of the supernatural begins?

All mundane events are the results of the operation of law. Every movement in the skies or upon the earth proclaims to us that the universe is under government.

But if we admit that this is the case, from the mote that floats in the sunbeam to multiple stars revolving round each other, are we willing to carry our principles to their consequences, and recognize a like operation of law among living as

Law in the Inorganic and Organic Worlds.

among lifeless things,-in the organic as well as the inorganic world? What testimony does physiology offer on this point? Physiology, in its progress, has passed through the same And to the organic phases as physics. Living beings have been considered as world. beyond the power of external influences, and, conspicuously among them, Man has been affirmed to be independent of the forces that rule the world in which he lives. Besides that immaterial principle, the soul, which distinguishes him from all his animated companions, and makes him a moral and responsible being, he has been feigned, like them, to possess another immaterial principle, the vital agent, which, in a way of its own, carries forward all the various operations in his economy.

to man.

But when it was discovered that the heart of man is con- Especially structed upon the recognized rules of hydraulics, and with its great tubes is furnished with common mechanical contrivances, valves; when it was discovered that the eye has been arranged on the most refined principles of optics, its cornea, and humours, and lens properly converging the rays to form an image,—its iris, like the diaphragm of a telescope or microscope, shutting out stray light, and regulating the quantity admitted; when it was discovered that the ear is furnished with the means of dealing with the three characteristics of sound, its tympanum for intensity, its cochlea for pitch, its semicircular canals for quality; when it was seen that the air brought into the great air-passages by the descent of the diaphragm, calling into play atmospheric pressure, is conveyed upon physical principles into the ultimate cells of the lungs, and thence into the blood, producing chemical changes throughout the system, disengaging heat, and permitting all the functions of organic life to go on; when these facts and very many others of a like kind were brought into prominence by modern physiology, it obviously became necessary to admit that animated beings do not constitute that exception once supposed, and that organic operations are the result of physical agencies.

If thus, in the recesses of the individual economy, these natural agents bear sway, must they not operate in the social economy too?

In social as well as in

dividual life.

Effects of the seasons

6

Dominion of Law in Social Life.

Has the great shadeless desert nothing to do with the habits of the nomade tribes who pitch their tents upon itthe fertile plain no connection with flocks and pastoral life -the mountain fastnesses with the courage that has so often defended them-the sea with habits of adventure?

Indeed, do not all our expectations of the stability of social institutions rest upon our belief in the stability of surrounding physical conditions? From the time of Bodin, who nearly three hundred years ago published his work, 'De Republica,' these principles have been well recognized, -that the laws of Nature cannot be subordinated to the will of Man, and that government must be adapted to climate. It was these things which led him to the conclusion that force is best resorted to for northern nations, reason for the middle, and superstition for the southern.

In the month of March the sun crosses the equator, dison animals pensing his rays more abundantly over our northern hemiand plants. sphere. Following in his train, a wave of verdure expands

towards the pole. The luxuriance is in proportion to the local brilliancy. The animal world is also affected. Pressed forward or solicited onward by the warmth, the birds of passage commence their annual migration, keeping pace with the developing vegetation beneath. As autumn comes on, this orderly advance of light and life is followed by an orderly retreat, and in its turn the southern hemisphere presents the same glorious phenomenon. Once every year does the life of the earth pulsate; now there is an abounding vitality, now a desolation. But what is the cause of all this? It is only mechanical. The earth's axis of rotation is inclined to the plane of her orbit of revolution round the sun.

Let that wonderful phenomenon and its explanation be a lesson to us; let it profoundly impress us with the importance of physical agents and physical laws. They intervene in the life and death of man personally and socially. External events become interwoven in our constitution; their periodicities create periodicities in us. Day and night are incorpo

rated in our waking and sleeping; summer and winter compel us to exhibit cycles in our life.

Existence depends on Physical Conditions.

7

existence

They who have paid attention to the subject have long ago Individual ascertained that the possibility of human existence on the depends on physical earth depends on conditions altogether of a material kind. conditions. Since it is only within a narrow range of temperature that life can be maintained, it is needful that our planet should be at a definite mean distance from the source of light and heat, the sun; and that the form of her orbit should be so little eccentric as to approach closely to a circle. If her mass were larger or less than it is, the weight of all living and lifeless things on her surface would no longer be the same; but absolute weight is one of the primary elements of organic construction. A change in the time of her diurnal rotation, as affecting the length of the day and night, must at once be followed by a corresponding modification of the periodicities of the nervous system of animals; a change in her orbital translation round the sun, as determining the duration of the year, would, in like manner, give rise to a marked effect. If the year were shorter, we should live faster and die

sooner.

vegetable

balanced by

conditions.

In the present economy of our globe, natural agents are Animal and relied upon as the means of regulation and of government. life interThrough heat, the distribution and arrangement of the material vegetable tribes are accomplished; through their mutual relations with the atmospheric air, plants and animals are interbalanced, and neither permitted to obtain a superiority. Considering the magnitude of this condition, and its necessity to general life, it might seem worthy of incessant Divine intervention, yet it is in fact accomplished automatically.

appear

sances and

determined.

Of past organic history the same remark may be made. And also The condensation of carbon from the air, and its inclusion in the strata, constitute the chief epoch in the organic life of extinctions the earth, giving a possibility for the appearance of the hotblooded and more intellectual animal tribes. That great event was occasioned by the influence of the rays of the sun. And as such influences have thus been connected with the appearance of organisms, so likewise have they been concerned in the removals. Of the myriads of species which have become extinct, doubtless every one has passed

Perma

nence of organisms due to im

conditions.

8

Origin, Variation, and Extinction of Species. away through the advent of material conditions incompatible with its continuance. Even now, a fall of half-a-dozen degrees in the mean temperature of any latitude would occasion the vanishing away of the forms of warmer climates, and the advent of those of the colder. An obscuration of the rays of the sun for a few years would compel a redistribution of plants and animals all over the earth many would totally disappear, and everywhere new-comers would be seen.

The permanence of organic forms is altogether dependent on the invariability of the material conditions under which mobility of they live. Any variation therein, no matter how insignifiexternal cant it might be, would be forthwith followed by a corresponding variation in the form. The present invariability of the world of organization is the direct consequence of the physical equilibrium; and so it will continue, as long as the mean temperature, the annual supply of light, the composition of the air, the distribution of water, oceanic and atmospheric currents, and other such agencies remain unaltered; but if any one of these, or of a hundred other incidents that might be mentioned, should suffer modification, in an instant the fanciful doctrine of the immutability of species would be brought to its true value. The organic world appears to be in repose, because natural influences have reached an equilibrium. A marble may remain for ever motionless upon a level table; but let the surface be a little inclined, and the marble will quickly run off. What should we say of him who, contemplating it in its state of rest, asserted that it was impossible for it ever to move?

They who can see no difference between the racehorse and the Shetland pony, the bantam and the Shanghai fowl, the greyhound and the poodle dog, who altogether deny that impressions can be made on species, and see in the long succession of extinct forms, the ancient existence of which they must acknowledge, the evidences of a continuous and creative Orderly se- intervention, forget that mundane effects observe definite conditions sequences, event following event in the necessity of the case, is followed by orderly and thus constituting a chain, each link of which hangs on a organic changes preceding, and holds a succeeding one. Physical influences

quence of

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