Peter Kropotkin and John Thomas Bealby, 1911 Encyclopædia Britannica (1911)
“ Climatic, Geo-Botanical and Geo-Zoological Importance.—The importance of the Urals as a climatic and geo-botanical boundary can no longer be regarded as very great. Most European species of plants freely cross the Urals into Siberia, and several Siberian species travel across them into northern Russia. But, being a zone of hilly tracts extending from north to south, the Ural Mountains necessarily exercise a powerful influence in pushing a colder northern climate, as well as a northern flora and fauna, farther south along their axis. ”
