121 : 4. See the note top. 128 : 2. 121 : 15. F. Keller, _The Lake-Dwellings of Switzerland and Other Parts of Europe_; Schenck, _La Suisse préhistorique_, pp. 533–549; G. and A. de Mortillet, _Le Préhistorique_, part 3, and Munro, _The Lake Dwellings of Europe_. The lake-dwelling, known as Pont de la Thièle, between the lakes of Bienne and Neuchâtel, according to Grilliéron’s calculations, is dated 5000 B. C. See Keller, p. 462; Lyell, Antiquity of Man, p. 29; Avebury, _Prehistoric Times_, p. 401; and De Mortillet, _Le Préhistorique_, p. 621. 121 : 17. Schenck, p. 190, says concerning Switzerland: “There were three [cultural] stages, stone, bronze, and iron.... On the other hand, from the anthropological point of view, this subdivision can also be made. In the first stage [Neolithic Lacustrian], we find only brachycephalic crania; in the second there are an almost equal number of brachycephalic and dolichocephalic; in the third there is a predominance of dolichocephalic” (that is, Schenck divides the Neolithic into three periods according to skulls, and the last runs into the age transitionary to bronze). See also G. Hervé, _Les populations lacustres_, p. 140; His and Rütimeyer, _Crania Helvetica_, pp. 12, 34, etc.; and the note on p. 275 of Rice Holmes’s _Cæsar’s Conquest of Gaul_. Ripley gives useful and concise discussions on pp. 120, 471, 488 and 501. 121 : 19. See both Keller and Schenck for the numbers of dwellings. 121 : 22. _There were, of course, the caves and rock shelters used during a large part of the year, but probably no other regularly constructed dwellings served as permanent, all-the-year-round places of abode prior to the lake dwellings, and it is doubtful if these were inhabited in winter. It is generally believed that the custom of building pile villages arose from considerations of safety. This protection would be absent when the lakes were frozen over, and at the same time the huts would be exposed on all sides, including the floor, to the wintry blasts sweeping the lakes. They would in this way be rendered practically uninhabitable during the winter season._ Keller declares that the same type of dwelling is found in the whole circle of countries which were formerly Celtic. (Introduction, p. 2.) The Crannoges of Scotland and Ireland continued in use until the age of iron in those countries. In Switzerland the lake dwellings disappeared about the first century (p. 7). The population was numerous (p. 432), large enough to have to depend upon cattle and agriculture (p. 479).