220 A BOOK-LOVER'S HOLIDAYS 



bases of which flourish animals characteristic of 

 the tropical Mexican plateau ; the former having 

 been left stranded on high mountain islands 

 when, with the retreat of the glaciers, the cli- 

 mate of the United States grew warmer and 

 the tide of southern life-forms swept northward 

 over the lowlands. Under such conditions the 

 same river deposits might show a combination 

 of utterly different faunas. Moreover, some 

 modern animals are found from the arctics to 

 the tropics. The American lynx extends, in 

 closely connected forms, from the torrid deserts 

 of Mexico to arctic Alaska; so does the moun- 

 tain-sheep. The tiger flourishes in the steaming 

 Malay forests and in snowy Manchuria. I have 

 found the cougar breeding in the frozen, bitter 

 midwinter among the high Rockies, in a coun- 

 try where snow covered the ground for six 

 months, and where the caribou would be en- 

 tirely at home; and again in Brazil under the 

 equator, in the atmosphere of a hot-house. 

 There were periods, during the ages before his- 

 tory dawned, but when man had long dwelt in 

 Europe, in which herds of reindeer may have 

 roamed the French and English uplands within 

 sight of rivers wherein the hippopotamus dwelt 

 as comfortably as he recently did at the Cape 

 of Good Hope. 



