PLANT ARCHEOLOGY. 273 



vierges du Br^sil et de Java, aux valines profondes du Ni^paul, aux 

 savanes noy^es de I'Ordnoque, oil la vie surabonde, ou une lumiere 

 ardente, vive et dor^e, ondule de toutes parts, souleve de tiedes 

 vapeurs, joue avec Tombre, et fait resplendir les formes des plus 

 merveilleux vdg^taux ! Sous les tropiques, I'homme se sent ecras^ 

 par une vie exuberante, il lutte incessament pour maintenir sa place 

 au milieu de la nature, dout il est doming ; ses plus fortes oeuvres sont 

 envahies en peu de temps ; les arbres imraenses reprennent possession 

 du sol, des que celui-ci est abandonn^ a lui-meme. Dans I'extreme 

 Nord, la faiblesse de Thomme est encore plus ^vidente, mais c'est 

 du poids de la nature inerte qu'il est accabl^. Les elements regnent 

 seuls dans ces regions d^vast^es, oil I'atmosphere se trouve livr^e a 

 d'^pouvantables tourmentes. La neige derobe les asperites du sol, la 

 glace couvre la mer d'un sol factice, souvent mobile et tou jours dan- 

 gereux ; la confusion est partout, le calme nulle part ; chaque pas est 

 penible, la vie elle-meme devient un effort que I'energie la mieux 

 trempee ne pent soutenir longtemps sans succomber." (p. 212.) 



The modifications of this contrast through the actual dis- 

 tribution of land and water, winds and currents, are then con- 

 sidered. As these have a fixity secondary only to the funda- 

 mental elements of climate, — namely, the heat of the sun, the 

 inclination of the earth's axis to the plane of its orbit, and 

 the relative density of the atmosphere according to the eleva- 

 tion of the land-surface, — the climate of any part of the world 

 might be supposed to have been constant, oscillations excepted, 

 through the long periods that have elapsed since existing 

 species or their immediate ancestors were introduced. It is 

 not very long ago that Arago demonstrated, to his own and 

 the general satisfaction, that there has been no appreciable 

 chano'e of the earth's climate in man's time. Plants are the 

 thermometers of the ages, by which climatic extremes and 

 climates in general through long periods are best measured. 

 For at least five or six thousand years the Vine and the Date- 

 palm have grown in proximity, and have furnished grapes 

 and dates to the inhabitants of the warmer shores of the 

 Mediterranean. Yet a very moderate change either way in 

 the temperature woidd have excluded the one or the other. 

 So Arago concluded that man had witnessed no sensible 

 changes in the climate of Europe ; a good conclusion, if re- 



