The seven day period is also a natural, physical one, whose influence is felt widely by vertebrate and invertebrate animals, as Darwin has pointed out,[240] and hence its appearance among these people, who lived entirely subject to the operation of their physical surroundings, is not so surprising. The most complete account of the Delaware tradition is that preserved by Heckewelder. In his pages it appears, not as a reminiscence of tribal history, but as the tradition of the whole eastern Algonkin race, and it claims for the three Delaware tribes an antiquity of organization surpassing that of any of their neighbors. It holds such an important place that I quote all the essential passages:-- "The Lenni Lenape (according to the traditions handed down to them by their ancestors) resided many hundred years ago in a very distant country in the western part of the American continent. For some reason, which I do not find accounted for, they determined on migrating to the eastward, and accordingly set out together in a body. After a very long journey, and many nights' encampments by the way, they at length arrived on the _Namoesi Sipu_, where they fell in with the Mengwe, who had likewise emigrated from a distant country, and had struck upon this river somewhat higher up. Their object was the same with that of the Delawares; they were proceeding on to the eastward, until they should find a country that pleased them. The spies which the Lenape had sent forward for the purpose of reconnoitring, had long before their arrival discovered that the country east of the Mississippi was inhabited by a very powerful nation, who had many large towns built on the great rivers flowing through their land. Those people (as I was told) called themselves Talligeu or Talligewi. Colonel John Gibson, however, a gentleman who has a thorough knowledge of the Indians, and speaks several of their languages, is of opinion that they were not called Talligewi, but Alligewi. * * * "Many wonderful things are told of this famous people. They are said to have been remarkably tall, and stout, and there is a tradition that there were giants among them, people of a much larger size than the tallest of the Lenape. It is related that they had built to themselves regular fortifications or entrenchments, from whence they would sally out, but were generally repulsed. * * * "When the Lenape arrived on the banks of the Mississippi, they sent a message to the Alligewi to request permission to settle themselves in their neighbourhood. This was refused them, but they obtained leave to pass through the country and seek a settlement farther to the eastward. They accordingly began to cross the Namaesi Sipu, when the Alligewi, seeing that their numbers were so very great, and in fact they consisted of many thousands, made a furious attack on those who had crossed, threatening them all with destruction, if they dared to persist in coming over to their side of the river. * * *