386 SCIENCE PROGRESS 



temperate and sub-arctic plants), and it seems possible that the 

 Wolvercote horizon may correspond to one of the warmer minor 

 undulations which filled the interval between the great cold 

 waves of the third and fourth glacial epochs ; we might then 

 represent the succession by the following scheme : 



Contorted gravel .... glacial episode IV. 



Wolvercote bouchers (Oxfordian) temperate climate. 



,, ,, „ cold climate? 



Acheulean of Hoxne . . . temperate climate. 



Betula nana beds of Hoxne . . cold climate. 



Alder beds of Hoxne (Chellean ?) temperate climate. 



Chalky boulder clay . . . glacial episode III. 



The stratigraphical relations of the older industries have been 

 investigated by Prof. Rutot. 



One of the motives for writing the preceding articles was the 

 belief that the chronology of the palaeolithic industries had at 

 length been placed on a sound basis through the investigations 

 of Prof. Penck ; now, with the progress of discovery, we are 

 again beset with doubts. In spite of the persistent efforts of 

 gifted observers, extending over many years, the history of 

 the Pleistocene epoch, especially those parts of it concerned 

 with the evolution of the human race, still remains an open 

 question. 



The progress of artificial excavations is, however, constantly 

 affording fresh material for study, and with the increasing 

 accumulation of evidence the day cannot be far distant when 

 the later stages of human evolution will be provided with such 

 dates as the stratified sequence can supply ; and it is even 

 possible that in the remote future these may be brought into 

 some connection with the recognised standard of time. This 

 hope is stimulated by the fact that our knowledge has been 

 increased even so recently as within the last twelve months by 

 three discoveries of great importance. 



We may refer first to the beautifully preserved lower jaw of 

 a palaeolithic man {Homo Heidelbcrgensis), found by Dr. Schoeten- 

 sack at Mauer, 10 kilometres south-east of Heidelberg. This is 

 evidently of great antiquity. It was extracted from a bed of 

 fluviatile sand exposed in a sand-pit at a depth of 24 metres 

 (say 80 feet) from the surface. The section exposed in the pit 

 is as follows : 



