To those who are familiar with the vast lapse of time required by the geological history of the earth, it may be startling to ascribe the whole of it to three or four of the creative days. If, however, it be admitted that these days were periods of unknown duration, no reason remains for limiting their length any farther than the facts of the case require. If in the strata of the earth which are accessible to us we can detect the evidence of its existence for myriads of years, why may not its Creator be able to carry our view back for myriads more. It may be humbling to our pride of knowledge, but it is not on any scientific ground improbable, that the oldest animal remains known to geology belong to the middle period of the earth's history, and were preceded by an enormous lapse of ages in which the earth was being prepared for animal existence, but of which no records remain, except those contained in the inspired history. It would be quite unphilosophical for geology to affirm either that animal life must always have existed, or that its earliest animals are necessarily the earliest organic beings. To use, with a slight modification, the words of an able thinker on these subjects,[88] "For ages the prejudice prevailed that the historical period, or that which is coeval with the life of man, exhausted the whole history of the globe. Geologists removed that prejudice," but must not substitute "another in its place, viz., that geological time is coeval with the globe itself, or that organic life always existed on its surface."