354 AECH^OLOGY. 



Leman. There have been also recognized traces of villages of the 

 same age on different points of the alluvial deposits of the Neuchatel 

 basin: at the mouths of the Mantua and the Reuse; in the midst of 

 the marsh of the Thiele, and chiefly in the marshy valley of the Orbe, 

 which stretches to the south of the town of Yverdun. In order to 

 know the age of these piles buried under the deposits of alluvium, it 

 suffices to measure the distance which separates the present bank 

 from the ancient one, and to find between these two concentric lines 

 a given point of which the age is known, and which may furnish an 

 approximate estimate of the rate of progress of the alluvium. This 

 point exists in the valley of the Orbe : it is the site of the ruins of 

 the ancient gallo-Roman city of Eburodunum. Between the down on 

 which they rest and the lake, on the space partly occupied by the 

 town of Yverdun, there is found no vestige of Roman antiquities; 

 and we may thence conclude that, at the commencement of our era, 

 the shore of the lake approached much more nearly to the foot of the 

 down. Admitting that its waters bathed the walls of the castrum 

 ehurodunense, it would have required at least fifteen centuries for the 

 formation of the zone of 800 metres in extent, which lies between 

 the ruins and the shore; but it is highly probable that the retreat of 

 the waters has not been so rapid, for the Celtic name of Eburodunum 

 testifies in favor of a more ancient establishment than that of the 

 Romans. However, if we accept as a point of comparison this datum 

 of fifteen centuries, (evidently too little,) we perceive that another 

 period of eighteen centuries must have been necessary for the filling 

 up of the space of 1,000 metres which separates the down from the 

 ancient piles situated to the south, at the base of the hillock of 

 Chamblon: thus we are carried back to the fifteenth century before 

 ^ur era. At the latest it was at this epoch, and, perhaps, long be- 

 fore, that the lacustrian village of Chamblon, invaded by the turf 

 and the alluvium of the Orbe, must have been abandoned by its in- 

 habitants. In order to arrive at the epoch of the foundation, it is 

 still necessary to ascend the course of ages, and to add some centu- 

 ries for the filling up of the strait which separated the village from 

 the ancient shore, still easily recognizable at the foot of the isolated 

 little hill. While acknowledging that these figures establish nothing 

 absolutely, M. Troyon is led to fix the construction of the lacustrian 

 habitations of Chamblon by the primitive colonists of Helvetia at two 

 thousand years before the Christian era. It might, perhaps, be ob- 

 jected that the level of the lake may have sunk considerably during 

 the historic ages, and have left dry the marshy plain of Yverdun; 

 but the ancient shore is situated at exactly the same height with the 

 present shore. The level of the lake has, therefore, remained the 

 same during the last forty centuries of history. 



The result to which M. Troyon has been conducted by the exami- 

 nation of the alluvial deposits of the valley of the Orbe seems to us 

 one of the greatest triumphs of geology. This science, which had 

 already taught us the relative age of the fossil plants and animals of 

 our globe, serves now to determine the critical chronology of the 

 races of men which have succeeded one another on the surface of the 



