Travelers in Alaska find local changes of climate evidently very rapid in comparison with such changes in more temperate regions. Parts of the country that a hundred years ago were covered by ice sheets now have young forests growing thriftily over them; while tracts of country now ice covered, or covered by glacial drift, were certainly covered by luxuriant vegetation within the century. The changing character of the ice sheets bring corresponding changes in atmospheric currents, and thus parts of the country not so cold but that forest trees could grow well, find themselves under temperatures fatal to arboreal life. Hence dead forests are common, and living forests spring up in other places where only dead forests existed for years before. The heavy air - made heavy by cooling when coming in contact with the ice sheets - rolls down toward the equator, from whence the warmer and lighter air from the higher currents flows in to fill the vacuum caused by southern flow of the heavy column. Hence trees and vegetation skirt the edges of the ice sheets, except in the deeper channels and gulches through which the heavy cold air flows.

Thus it is that as a glacier flows or recedes, a ravine which in one age is the channel for a continuous Arctic current, may be the channel for a warm current in another. Alaska furnishes an admirable field for the study of these rapid changes in local climate, and enables us to understand much of Arctic phenomena that seems mysterious in the Old World. It is reported that not many centuries ago, the northern part of Iceland and Greenland was cultivable, but that a change of climate occurred that rendered such culture impracticable. Scientific men usually use the word " reported " when referring to this fact, and facts are continually being placed on record as they may seem to bear for or against this statement. Recently it has been recorded that in Iceland, at the station known as Akureyi, there are a few trees existing of the mountain ash, Sorbus aucuparia, that are very old and about 25 feet high, while smaller trees, with birches and other things, cannot now get beyond the stature of dwarf bushes; and it is assumed, and with good reason as Alaskan experience affords, that these survived the cold currents that destroyed all other of their friends and neighbors.

The coal, too, is simply lignite of comparatively modern origin, and formed of species of Populus now existing on the American continent, but which seems to have been wholly swept away by the deluge of cold air which overspread these regions. The facts are particularly interesting to science as showing that geological periods, as they may be termed, are likely to be much shorter in the Arctic than in the temperate regions - that data collected in one part of the world may not have the same interpretation in the other - and that the rolling away of cold, heavy air toward the equator, may, by the lighter warm air that must fill the vacuum, necessitate a higher temperature and possibly an open sea at the poles. - Independent.