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leave it the seat of a powerful nation. Changes so important 
as these are not effected in a day ; the progress of the human 
mind is but slow ; and the gradual additions to human know- 
ledge and power, like the rings in trees, enable us to form 
some idea how distant must be the date of their commence- 
ment. So varied however are the conditions of the human 
mind, so much are all nations affected by the influence of 
others, that when we attempt to express our impressions, so 
to say, in terms of years, we are baffled by the complexity of 
the problem, and can but confess our ignorance. Occasionally 
indeed we obtain a faint glimmer of light, but the result is 
only to show us obscurely a long vista, without enabling us to 
define any well-marked points of time. Thus in Denmark we 
found three periods of arborescent vegetation, corresponding 
to the three epochs of human development, and we know that 
the extermination of one species of forest tree and its replace- 
ment by another is not the work of a day. The Swiss archae- 
ologists, however, have attempted to make an estimate 
somewhat more definite than this, founded on certain allu- 
vial deposits at the point where the Torrent of the Tiniere 
falls into the Lake of Geneva, near Villeneuve, from which 
M. Morlot deduces an antiquity of from 3,000 to 4,000 
years for the bronze period, and 5,000 to 7,000 years for 
the stone period. 
Far earlier, however, even than these are the remains 
discovered by M. Boucher de Perthes, and first described in 
a work " De l'industrie primitive, ou les arts et leur origine, ,, 
which appeared in the year 1846. In this he announced 
that he had found human implements in beds unmistakeably 
belonging to the age of the drift. In his "Antiquites 
Celtiques et Antediluviennes " (1847), he also gave numerous 
illustrations of these stone weapons, but unfortunately the 
figures were so small and rude, as scarcely to do justice to the 
originals. For seven years M. Boucher de Perthes made few 
