deposits becomes very confusing to those who have not the advantage of practically examining them in situ, on account of the irregularity of their respective depths, and the fact that one or more members of the series may be altogether absent. The accompanying section at Saint Acheul (Fig. 12), Carière Bultel (altitude 54 metres), drawn up by M. Comment, gives the succession and relative magnitude of the respective deposits at that locality.
FIG. 12. Section taken at Saint Acheul, Carière Bultel. (After Commont.)
These researches of M. Commont suggest problems of far-reaching significance. If the valley of the Somme, during its excavation, presented continuous and successive land-surfaces, yielding a flora and fauna sufficient to supply its Palæolithic races with the necessaries of life, it is clear that the geological and archaeological phenomena of the locality have not yet been fully understood. It cannot be supposed that the