There are also certain scientific considerations which oppose the view that the Flood was geographically universal. Not that science opposes any difficulty insuperable to the power of God; but it draws attention to a number of most extraordinary, if not miraculous phenomena involved in the admission of a geographically universal Deluge. First, no such geological traces can be found as ought to have been left by a universal Deluge; for the catastrophe connected with the beginning of the ice-age, or the geological deluge, must not be connected with the Biblical. Secondly, the amount of water required by a universal Deluge, as described in the Bible, cannot be accounted for by the data furnished in the Biblical account. If the surface of the earth, in round numbers, amounts to 510,000,000 square kilometres, and if the elevation of the highest mountains reaches about 9000 metres, the water required by the Biblical Flood, if it be universal, amounts to about 4,600,000,000 cubic kilo-metres. Now, a forty days’ rain, ten times more copious than the most violent rainfall known to us, will raise the level of the sea only about 800 metres; since the height to be attained is about 9000 metres, there is still a gap to be filled by unknown source. amounting to a height of more than 8000 metres, in order to raise the water to the level of the greatest mountains. Thirdly, if the Biblical Deluge was geographically universal, the sea water and the fresh water would mix to such an extent that neither the marine animals nor the fresh-water animals could have lived in the mixture without a miracle. Fourthly, there are serious difficulties connected with the animals in the ark, if the Flood was geographically universal: How were they brought to Noe from the remote regions of the earth in which they lived? How could eight persons take care of such an array of beasts? Where did they obtain the food necessary for all the animals? How could the arctic animals live with those of the torrid zone for a whole year and under the same roof? No Catholic commentator will repudiate an explanation merely for fear of having to admit a miracle; but no Catholic has a right to admit Biblical miracles which are not well attested either by 'Scripture or tradition. What is more, there are traces in the Biblical Flood story which favor a limited extent of the catastrophe: Noe could have known the geographical universality of the Deluge only by revelation; still the Biblical account appears to have been written by an eye-witness. If the Flood had been universal, the water would have had to fall from the height of the mountains in India to the level of those in Armenia on which the ark rested, i.e. about 11,500 feet, within the space of a few days. The fact that the dove is said to have found “the waters … upon the whole earth”, and that Noe “saw that the face of the earth was dried”, leaves the impression that the inspired writer uses the word “earth” in the restricted sense of “land”. Attention has been drawn also to the “bough of an olive tree, with green leaves” carried by the dove in her mouth on her second return to the ark.