The enormous length of the biogenetic periods (i.e., the periods during which organic life has been evolving on our planet) is still very differently estimated by geologists and paleontologists, astronomers and physicists, because the empirical data of the calculation are very incomplete and admit great differences of estimate. However, most modern experts aver that their length runs to 100 and 200 million years (some say double this, and even more). If we take the lesser figure of 100 millions, we find this distributed over the five chief periods of organic geology very much as is shown on Table 1. In order to get a clearer idea of the vast duration of these evolutionary periods, and to appreciate the relative shortness of the "historical period," Dr. H. Schmidt (Jena) has reduced the 100,000,000 years to a day. In this scheme the twenty-four hours of "creation-day" are distributed as follows over the five evolutionary periods:

If we put the length of the "historic period" at 6,000 years, it only makes five seconds of "creation-day"; the Christian era would amount to two seconds.