282 MAN'S PLACE IN THE GEOLOGICAL RECORD. 



sits and cave-earths imbedding ruder implements and re- 

 mains of the Irish deer, reindeer, and musk-ox, and from 

 these again to deeper river-gravels and brick-earths con- 

 taining implements still simpler in fashion, and associated 

 with the relics of mammoth and rhinoceros. Considerable 

 changes in the physical geography of Europe must have 

 taken place (as these silts and peat-growths imply) since 

 the time of the primitive horse and long-fronted ox ; still 

 greater must have taken place since the reindeer and musk- 

 ox found a suitable climate in the latitude of France and 

 England j and greater still since the mammoth roamed in 

 the pine forests and over the plains of the same regions. 

 Admitting the changes, the question remains, How shall 

 we estimate the lapse of time required for their fulfilment ? 

 If they are changes of a physical kind, we estimate accord- 

 ing to the rate at which similar changes are taking place 

 at the present day ; if of a vital kind, by the rate at which 

 extinctions and creations seem to have been effected in 

 former epochs ; and if of a kind involving the progress of 

 our own race, we know that civilisation in the long-run is 

 only arrived at, even under the most favourable circum- 

 stances, by slow and gradual stages. 



Guided by these methods, the pile-dwellings in lakes (the 

 pfahlbauten of Switzerland and the crannoges of Ireland 

 and Scotland*) carry us back to the earlier Celtic times, 

 and may range from two to four thousand years, but clearly 

 they are not of the vast antiquity some archaeologists have 

 imagined, and though pre-historic in Europe, may have been 

 contemporary with historical events in Egypt and Western 

 Asia. Estimated by the implement-scale, they belong alike 

 to the ages of iron, bronze, and stone, and mark the long 

 occupancy of South-western Europe by the same partially 

 civilised but gradually improving race. As regards the 

 * For an account of these Lake-dwellings, see note, p. 254. 



