The Ancient Life History of the Earth | Page 8

at a much earlier period than others. In the confederation of animated nature some races can boast of an immemorial antiquity, whilst others are comparative parvenus. We have also the clearest evidence that the animals and plants which now inhabit the globe have been preceded, over and over again, by other different assemblages of animals and plants, which have flourished in successive periods of the earth's history, have reached their culmination, and then have given way to a fresh series of living beings. We have, finally, the clearest evidence that these successive groups of animals and plants (faun? and flor?) are to a greater or less extent directly connected with one another. Each group is, to a greater or less extent, the lineal descendant of the group which immediately preceded it in point of time, and is more or less fully concerned with giving origin to the group which immediately follows it. That this law of "evolution" has prevailed to a great extent is quite certain; but it does not meet all the exigencies of the case, and it is probable that its action has been supplemented by some still unknown law of a different character.
We shall have to consider the question of geological "continuity" again. In the meanwhile, it is sufficient to state that this doctrine is now almost universally accepted as the basis of all inquiries, both in the domain of geology and that of pal?ontology. The advocates of continuity possess one immense advantage over those who believe in violent and revolutionary convulsions, that they call into play only agencies of which we have actual knowledge. We know that certain forces are now at work, producing certain modifications in the present condition of the globe; and we know that these forces are capable of producing the vastest of the changes which geology brings under our consideration, provided we assign a time proportionately vast for their operation. On the other hand, the advocates of catastrophism, to make good their views, are compelled to invoke forces and actions, both destructive and restorative, of which we have, and can have, no direct knowledge. They endow the whirlwind and the earthquake, the central fire and the rain from heaven, with powers as mighty as ever imagined in fable, and they build up the fragments of a repeatedly shattered world by the intervention of an intermittently active creative power.
It should not be forgotten, however, that from one point of view there is a truth in catastrophism which is sometimes overlooked by the advocates of continuity and uniformity. Catastrophism has, as its essential feature, the proposition that the known and existing forces of the earth at one time acted with much greater intensity and violence than they do at present, and they carry down the period of this excessive action to the commencement of the present terrestrial order. The Uniformitarians, in effect, deny this proposition, at any rate as regards any period of the earth's history of which we have actual cognisance. If, however, the "nebular hypothesis" of the origin of the universe be well founded--as is generally admitted--then, beyond question, the earth is a gradually cooling body, which has at one time been very much hotter than it is at present. There has been a time, therefore, in which the igneous forces of the earth, to which we owe the phenomena of earthquakes and volcanoes, must have been far more intensely active than we can conceive of from anything that we can see at the present day. By the same hypothesis, the sun is a cooling body, and must at one time have possessed a much higher temperature than it has at present. But increased heat of the sun would seriously alter the existing conditions affecting the evaporation and precipitation of moisture on our earth; and hence the aqueous forces may also have acted at one time more powerfully than they do now. The fundamental principle of catastrophism is, therefore, not wholly vicious; and we have reason to think that there must have been periods--very remote, it is true, and perhaps unrecorded in the history of the earth--in which the known physical forces may have acted with an intensity much greater than direct observation would lead us to imagine. And this may be believed, altogether irrespective of those great secular changes by which hot or cold epochs are produced, and which can hardly be called "catastrophistic," as they are produced gradually, and are liable to recur at definite intervals.
Admitting, then, that there is a truth at the bottom of the once current doctrines of catastrophism, still it remains certain that the history of the earth has been one of law in all past time, as it is now. Nor need we shrink back affrighted at the vastness of the conception--the vaster for its