270 THE COLONIZATION OF NEW ENGLAND. 



A recent writer in the American Naturalist, Mr. 

 Grote, has drawn a picture of the way in which, 

 like many plants peculiar to the same alpine 

 heights, it was left behind on the retreat of the 

 glacial covering of the continent. " Year after 

 year," he says, " the great glacier retreated 

 farther and farther north, followed by the main 

 body of its train, plants, butterflies and animals, 

 the while some of these foolish butterflies were 

 beguiled by the shallow ice-rivers, which then 



FIG. 19?. Oeneis semidea, nat. size ; the under surface on right (Harris). 



filled the ravines of Mount Washington. Return 

 became at length impossible. They advanced 

 behind the descending local glaciers, step by step 

 up the mountain-side, pushed up from below by 

 the warm climate, which to them was uncon- 

 genial, until they reached the mountain-peak, 

 now bare of snow in the short summer. Here, 

 blown side wise by the wind, they patiently 

 cling to the rocks. Or, in clear weather, on weak 

 and careful wing, they fly from flower of stemless 

 mountain pink to blueberry, swaying from their 



