112 THE POPULAR SCIENCE MONTHLY. 



course with their unknown and unsuspected fellow-creatures else- 

 where. 



Not only has the Glacial epoch left these organic traces of its 

 existence, however ; in some parts of New Hampshire where the 

 glaciers were unusually thick and deep, fragments of the prime- 

 val ice itself still remain on the spots where they were originally 

 stranded. Among the shady glens of the White Mountains there 

 occur here and there great masses of ancient ice, the unmelted 

 remnant of primeval glaciers ; and one of these is so large that 

 an artificial cave has been cleverly excavated in it, as an attrac- 

 tion for tourists, by the canny Yankee proprietor. Elsewhere the 

 old ice-blocks are buried under the debris of moraine-stuff and 

 alluvium, and are only accidentally discovered by the sinking of 

 what are locally known as ice-wells. No existing conditions can 

 account for the formation of such solid rocks of ice at such a 

 depth in the soil. They are essentially glacier-like in origin and 

 character ; they result from the pressure of snow into a crystal- 

 line mass in a mountain valley ; and they must have remained 

 there unmelted ever since the close of the Glacial epoch, which, 

 by Dr. Croll's calculations, must most probably have ceased to 

 plague our earth some eighty thousand years ago. Modern 

 America, however, has no respect for antiquity ; and it is at pres- 

 ent engaged in using up this palseocrystic deposit — this belated 

 storehouse of prehistoric ice— in the manufacture of gin slings 

 and brandy cocktails. 



As one scales a mountain of moderate height— say seven or 

 eight thousand feet — in a temperate climate, one is sure to be 

 struck by the gradual diminution as one goes in the size of the 

 trees, till at last they tail off into mere shrubs and bushes. This 

 diminution — an old commonplace of tourists — is a marked char- 

 acteristic of mountain plants, and it depends, of course, in the 

 main upon the effect of cold, and of the wind in winter. Cold, 

 however, is by far the more potent factor of the two, though it 

 is the least often insisted upon ; and this can be seen in a mo- 

 ment by any one who remembers that trees shade off in just the 

 self-same manner near the southern limit of permanent snow in 

 the arctic regions. And the way the cold acts is simply this : it 

 nips off the young buds in spring in exposed situations, as the 

 chilly sea-breeze does with coast plants, which, as we commonly 

 but incorrectly say, are " blown sideways " from seaward. 



Of course, the lower down one gets, and the nearer to the soil, 

 the warmer the layer of air becomes, both because there is greater 

 radiation and because one can secure a little more shelter. So, 

 very far north, and very near the snow-line on mountains, you 

 always find the vegetation runs low and stunted. It takes advan- 

 tage of every crack, every cranny in the rocks, every sunny little 



