The work done within a few years upon the glaciers of Arctic America has proved peculiarly fruitful in results. Here, again, the whole subject is reviewed historically, and the name and work of each observer are impartially noted. Much of the difficulty encountered by the glacial theory arose, as we have seen, from the fact that only mountain glaciers had been studied, so that many of the phenomena produced by continental ice could not be explained. Professor Fairchild says, as to this aspect: "More has been learned of the structure, behavior, and work of our ancient ice sheets by the study of the Alaskan glaciers during the last ten years, and especially by the study of the Greenland ice cap during the last four years, than by all the study of the Alpine glaciers for the seventy years since they have been observed." Prominent among those who have worked in this field are the names of Professors Chamberlain and Salisbury in Greenland, and Professors H. F. Reid and I. C. Russell in Alaska; other important contributors are Prof. W. P. Blake, the pioneer geologist in Alaska, 1867; Dall and Baker, who discovered and named the Malaspina Glacier in 1874; and John Muir, 1878, for whom the Muir Glacier was named; Wright, Baldwin, Schwatka, Libbey, and others, and Barton and Tarr in Greenland. Professor Russell, in 1891, recognized and named a type of glacier that was before unknown. In his studies on the Malaspina he found a condition that does not occur, so far as yet observed, anywhere else than on the northwest coast of America; this is where a number of mountain glaciers debouch upon a low, flat coast plain, and unite to form a great sluggishly moving sheet of ice. This particular development he called the Piedmont type. In closing his address, Professor Fairchild remarks that the word "theory," as applied to the glacial origin of the drift and its phenomena, may and should now be abandoned. The subject has passed beyond the stage of theory, and is as well understood and as clearly established as the volcanic origin of the cone of Vesuvius or the sedimentary origin of stratified rocks. * * * * *