THE ORIGIN AND ANTIQUITY OF MAN 51 



was found imbedded many feet below the surface in 

 undisturbed beds of sand or gravel and geologists tell us 

 the age of the sand bed, the age of the remains must be at 



FIGURE 13. An infant, three weeks old, supporting its 

 own weight for over two minutes. The attitude of 

 the lower limbs, feet, and toes is strikingly simian. 



least as old as the sand bed. Geologists are able to esti- 

 mate with approximate accuracy the age of certain de- 

 posits of sand or gravel by determining the rate at which 

 similar beds are being formed at the present day through 

 the agency of rivers or glaciers. In this way we may be 

 certain of the age of these remains within a negligible 

 error. It is to be remembered that geologists measure 



