But the literature on this subject is so controversial and has attained such proportions, that the attempt to present current views will be limited to the discussion of the appended table (B). Here an endeavour has been made to submit the views expressed by the most competent observers of the day. The first point to which attention is directed consists in the manner in which the several glacial periods are distributed over the geological time-table. Boule claims one glaciation of Pliocene antiquity, followed by two Pleistocene glaciations. The remaining authors agree in ascribing all the glaciations to the Pleistocene period. Herein they follow the lead of Professor Penck, whose diagram of the oscillations in level of the snow-line in Central Europe is reproduced in Fig. 25. In the next place, the fact that Professor Penck's scheme was primarily intended to serve for the Swiss Alps must not be overlooked. That this system should leave traces everywhere else in Europe is not necessarily implied in accepting the scheme just mentioned. TABLE B. _List of types of associated implements._ +------------------------+-------------+-------------+--------------+ | | 1908 | 1908 | 1903 | | Penck's scheme[1] +-------------+-------------+--------------+ | | Boule[2] | Penck | Hoernes | +------------------------+---- -------+-------------+--------------+ | Postglacial =4= = with | Magdalenian | Magdalenian | -- | | Achen and other | Solutréan(4)| | | | oscillations (Penck) | | | | | |=============++ | | | =Glacial IV= 2nd | Mousterian || Solutréan | -- | | Pleistocene(2) | || [4] | | | Glaciation of Boule. | ++============++ | | "Würmian" of Penck | | || | | | | || | | _Interglacial_ =3= | Acheulean | Mousterian || Magdalenian | | = Riss-Würm interval | (Obermaier) | (warm phase)|| | | (Penck) | Chellean | || | | | | || | | =Glacial III= 1st | Chellean | Mousterian || -- | | Pleistocene Glaciation | | (cold phase)|| | | of Boule. "Rissian" | | || | | of Penck | | || | | | | || | | _Interglacial_ =2= | ? | Acheulean || Solutréan | | = Mindel-Riss interval | | Chellean ++=============|