With her incalculable partner, the irrational male, she and her family wander from district to district. At times they settle under a rock-shelter or in a cave, and make footpaths from it to watering-places and hunting-grounds. Here and there a river is crossed by stepping-stones, and more than one ravine is spanned by branches and by a fallen tree. What is their attitude to these things? The windfall tree-bridge, like every other gift from Nature, is a bane to them as well as a boon, for it is a road open to dangerous animals; as such it is a thing to be guarded, and many a fight in its defence occurs, creating traditions of bravery which are long remembered. Further, as time goes on, and the progenitors of man become more human, the pressure of competitive life draws ever more and more attention to the incompleteness of natural bridges. For example, stepping-stones may be useless when they are needed most of all, in wet seasons and after storms; and the tree-bridge is so narrow that warriors cross it only one by one, so their slow attack gives a terrible advantage to a brave defence. These hindrances, so obvious and so unpleasant, make appeal to the inventive faculty that a few men possess. Not much is required. From four or five seedling ideas a great many improvements will grow; and now is the moment for us to choose a vague tentative date for the beginning of this gradual development. Most people are bored by prehistoric archæology, because its earlier periods are as undated as is the oblivion of coma. So a date in obscure history, however tentative it may be, is very helpful; the mind rests on it, somehow, anyhow, and feels that the lost legions of the dead years left some oases in the Saharas of ancient time. And this point is not the only one that concerns the general reader who _does_ generally read. In recent years the antiquity of handicraft has been extended very much by a “find” of eagle-beaked flint implements, with other tools, below the Pliocene deposits on the East Anglian Coast. The eagle-beaked flints are undoubtedly of human manufacture, and they carry back the ancient stone period of man to the Tertiary times. Sir Ray Lankester writes on this important subject, and his knowledge helps us a great deal, though we have to recover it from entangled sentences. For example[38]:--