HIGH LIFE. Ill 



conditions recur ; they follow tlie snow-line as the snow-line re- 

 cedes ever in summer higher north toward the pole or higher 

 vertically toward the mountain summits. And this bespeaks in 

 one way to the reasoning mind a very ancient ancestry. It shows 

 they date back to a very old and cold epoch. 



Let me give a single instance which strikingly illustrates the 

 general principle. Near the top of Mount Washington^ as afore- 

 said, lives to this day a little colony of very cold-loving and 

 mountainous butterflies, which never descend below a couple of 

 thousand feet from the wind-swept summit. Except just there, 

 there are no more of their sort anywhere about ; and as far as the 

 butterflies themselves are aware, no others of their species exist 

 on earth ; they never have seen a single one of their kind, save 

 of their own little colony. One might compare them with the 

 Pitcairn Islanders in the South Seas — an isolated group of Eng- 

 lish origin, cut off by a vast distance from all their congeners in 

 Europe or America. But if you go north some eight or nine 

 hundred miles from New Hampshire to Labrador, at a certain 

 point the same butterfly reappears, and spreads northward toward 

 the pole in great abundance. Now, how did this little colony of 

 chilly insects get separated from the main body and islanded, as 

 it were, on a remote mountain-top in far warmer Nevv^ Hamp- 

 shire ? 



The answer is, they were stranded there at the end of the Gla- 

 cial epoch. 



A couple of hundred thousand years ago, or thereabouts — 

 don't let us haggle, I beg of you, over a few casual centuries — the 

 whole of northern Europe and America was covered from end to 

 end, as everybody knows, by a sheet of solid ice, like the one 

 which Frithiof Nansen crossed from sea to sea on his own ac- 

 count in Greenland. For many thousand years, with occasional 

 warmer spells, that vast ice-sheet brooded, silent and grim, over 

 the face of the two continents. Life was extinct as far south as 

 the latitude of New York and London. No plant or animal sur- 

 vived the general freezing. Not a creature broke the monotony 

 of that endless glacial desert. At last, as the celestial cycle came 

 round in due season, fresh conditions supervened. Warmer 

 weather set in, and the ice began to melt. Then the plants and 

 animals of the subglacial district were pushed slowly northward 

 by the warmth after the retreating ice-cap. As time went on, 

 the climate of the plains got too hot to hold them. The summer 

 was too much for the glacial types to endure. They remained 

 only on the highest mountain-peaks or close to the southern limit 

 of eternal snow. In this way, every isolated range in either con- 

 tinent has its own little colony of arctic or glacial plants and 

 animals, which still survive by themselves, unaffected by inter- 



