But with all these similarities there are essential differences due to the place element and the time element. It is evident that the farming frontier of the Mississippi Valley presents different conditions from the mining frontier of the Rocky Mountains. The frontier reached by the Pacific Railroad, surveyed into rectangles, guarded by the United States Army, and recruited by the daily immigrant ship, moves forward at a swifter pace and in a different way than the frontier reached by the birch canoe or the pack horse. The geologist traces patiently the shores of ancient seas, maps their areas, and compares the older and the newer. It would be a work worth the historian's labors to mark these various frontiers and in detail compare one with another. Not only would there result a more adequate conception of American development and characteristics, but invaluable additions would be made to the history of society. Loria,[11:1] the Italian economist, has urged the study of colonial life as an aid in understanding the stages of European development, affirming that colonial settlement is for economic science what the mountain is for geology, bringing to light primitive stratifications. "America," he says, "has the key to the historical enigma which Europe has sought for centuries in vain, and the land which has no history reveals luminously the course of universal history." There is much truth in this. The United States lies like a huge page in the history of society. Line by line as we read this continental page from West to East we find the record of social evolution. It begins with the Indian and the hunter; it goes on to tell of the disintegration of savagery by the entrance of the trader, the pathfinder of civilization; we read the annals of the pastoral stage in ranch life; the exploitation of the soil by the raising of unrotated crops of corn and wheat in sparsely settled farming communities; the intensive culture of the denser farm settlement; and finally the manufacturing organization with city and factory system.[11:2] This page is familiar to the student of census statistics, but how little of it has been used by our historians. Particularly in eastern States this page is a palimpsest. What is now a manufacturing State was in an earlier decade an area of intensive farming. Earlier yet it had been a wheat area, and still earlier the "range" had attracted the cattle-herder. Thus Wisconsin, now developing manufacture, is a State with varied agricultural interests. But earlier it was given over to almost exclusive grain-raising, like North Dakota at the present time. Each of these areas has had an influence in our economic and political history; the evolution of each into a higher stage has worked political transformations. But what constitutional historian has made any adequate attempt to interpret political facts by the light of these social areas and changes?[12:1]