610 PEPORT OF NATIONAL MUSEUM, 1888. 



They have been called ia England drift implements, because they 

 have been found in the river drifts or deposits. Their position when 

 thus found indicates the same antiquity as the river valleys themselves. 

 There was a time when the rivers filled the valleys from hill to hill, 

 pouring down with a rush and carrying the greatest quantity of water 

 to the sea. In that time the irresistible current eroded the earth, and, 

 if need be, the rock, to make for itself a waterway. As time progressed 

 the water subsided more or less, and the current become slower and less 

 powerful. The sand and gravel which had before been carried out to 

 the sea began to be deposited here and there in this bend and on that 

 point, until the deposit came to the surface of the water and formed 

 what is now the highest terrace. Then the river was narrowed and the 

 terrace became a new river bank. This process was repeated again and. 

 again until the river finally retreated to its present bed, and left ter- 

 races, sometimes three in number, the first being higher, deeper, and 

 more distant from the river than the others. These are now the marks 

 of the successive stages in the formation of the river valleys. 



The sand and gravel deposit of the river at Chelles spreads out and 

 forms the plain of the river valley. It is from 22 to 26 feet in thick- 

 ness. The sand and gravel rests upon the original chalk, and is about 

 on a level with the highest floods of the river in modern times. These 

 deposits are of different degrees of fineness, and are laid in strata or 

 layers, showing that they were made by the action of water. The strata 

 are not always continuous, and dilferin thickness and jjosition, showing 

 that the water had varying currents. There are to be found occasional 

 huge blocks of erratic stone. The sand and gravel is sometimes in- 

 tercalated by other strata which could not have been laid down at the 

 same time or in corresponding manner. One of these is a stratum of 

 calcareous cement several inches in thickness. In many other places, 

 but nearer the top, are pockets or strata which contain various solu- 

 tions of iron, the percolating water from which gives the color to the 

 implement heretofore described. 



There have been many and great discussions over the formation of 

 these river valleys and the deposits of their sand and gravel. These 

 as to the time, manner of formation, and antiquity. I do not enter into 

 this discussion now. I merely state a fact on which all disputants 

 are agreed: that the implements of human industry belonging to this 

 epoch are found in these river gravels, in positions which indicate their 

 deposit at the time of the original formation and at a distance from the 

 river and depth below the surface which indicates their antiquity to 

 be equal with the first deposit. Whether they were swept down from 

 the springs which formed the headwaters of the river, were dropped on 

 the borders in the near neighborhood, or precisely in what manner 

 they became involved with the sand and gravel in which they are now 

 found, is not only unknown but there has as yet been developed no sat- 

 isfactory theory. 



