[Illustration: Lomaland Photo. and Engraving Dept. HAINES, ALASKA] [Illustration: Lomaland Photo. and Engraving Dept. AN ALASKAN VALLEY] [Illustration: Lomaland Photo. and Engraving Dept. AN ALASKAN GLACIER] GLACIATION, PAST AND PRESENT: by T. Henry The stupendous effects of ice in ages long gone by have been elaborately studied by geologists, who have given us fascinating descriptions thereof. The enormous power of ice as an agent in transforming the land is shown by the study of its doings at the present day. Much has been done in this direction in the Alps, but in America we have Alaska, which, besides the prospects of material resources which it holds out to the future, is already affording a fine field for the observer of nature. Here we may see glaciers at work; and though the action of the ice-sheet at its bottom is hid from view, what goes on at the advancing margin is evident from year to year, and even from day to day. All the phenomena of moraines, the pushing forward of rocks and trees, the damming up of valleys to form lakes, the scraping up of boulder-clay, the rounding-off of the rocks, etc., may be witnessed; together with many details that could not easily have been inferred from a study of the sites of past glaciation. One of the most interesting of these effects is the way in which the glacier acts indirectly through the force of the huge waves it produces when it enters a river. Vast blocks from the ice-front fall off with a splash and send up a wave and a series of waves that sweep over the bank and into the forest beyond, achieving more erosion than ever rain or river did. The greater erosive effects follow on brief sudden movements. In the _National Geographical Magazine_ (Washington) for June, 1911, there is a most interesting article recording the field-studies of the National Geographical Society in Alaska. Many of the glaciers which they studied had advanced during the last year or two, and others had been retreating. The reasons why some should advance while others retreat were not satisfactorily determined, and further study must precede a decision in this respect. But earthquakes, of which there were twenty-six days in September, 1899, are assigned a chief rôle. The effect of an earthquake was to produce a sudden advance and great but brief transformations. One of the largest glaciers in Yakutat Bay, the Nunatak, had changed a great deal since the year before. It had advanced decidedly, different parts of its front having come out 700 to 1000 feet up to June 17, 1910. From 1890 to 1909 the Nunatak Glacier receded steadily, going back over two miles and a half in this time.... The forward movement commenced between July 6, 1909 and June 1910. This was due to the accession of unusually large quantities of snow to the reservoirs of this glacier by avalanches during the twenty-six days of severe earthquakes of September, 1899. The size of glaciers is illustrated by the following description: