The incident of sending out birds to test the recession of the waters deserves notice, because of its apparently trivial nature, because it appears with variations in the Chaldean account, and because it has been treated in a remarkably unscientific manner by some critics. It indicates the uncertainty which would arise in the mind of the patriarch because of the fluctuating decrease of the waters, and possibly also a misty condition of the air preventing a distinct view of distant objects. The birds selected for the purpose were singularly appropriate. The raven is by habit a wanderer, and remarkable for power of flight and clearness of distant vision. So long, therefore, as it made the ark its headquarters, 'going and returning'[51] from its search for food, it might be inferred that no habitable land was accessible. The dove, sent out immediately after the raven,[52] is of a different habit. It could not act as a scavenger of the waters and go and return, but could leave only if it found land covered with vegetation. As a domesticated bird also, it would naturally come back to be taken into the ark. Hence it was sent forth at intervals of seven days, returning with an olive leaf when it found tree tops above the water, and remaining away when it found food and shelter. The Chaldean account adds a third bird, the swallow--a perfectly useless addition, since this bird, if taken into the ark at all, would from its habits of life be incapable of affording any information. This addition is a mark of interpolation in the Chaldean version, and proceeded perhaps from the sacred character attached by popular superstition to the swallow, or from the familiar habits of the bird suggesting to some later editor its appropriateness. Singularly enough, the usually judicious Schrader, probably from deficient knowledge of the habits of birds, fails to appreciate all this, and after a long discussion prefers the Babylonian legend for reasons of a most unscientific character, actually condemning the perfectly natural and clear Biblical story as artificial and due to a recent emendation. He says: 'When the story passed over to the Hebrews, the name of the swallow has disappeared,' and 'it is only from the Babylonian narrative that the selection of the different birds becomes clear.' This little disquisition of Schrader is, indeed, one of the most amusing instances of that inversion of sound criticism which results when unscientific commentators tamper with the plain statements of truthful and observant witnesses. [51] Margin of Authorised Version; less fully, 'to and fro' in the text. [52] There is no reason to suppose, as some have done, a hiatus here in the narrative.