Air, sunlight, and exercise are absolutely essential for the proper physical and intellectual development of human beings. Thoreau thought it necessary for people who wished to preserve their health and spirits to spend four hours a day in the open air, sauntering through the woods and over the hills and fields, free from all worldly engagements. No doubt he spoke from his own personal standpoint, and many persons do not require so much exercise in the open air as he did in order to preserve their health and spirits; but the proper observance of the laws of health certainly requires every one to spend a portion of every pleasant day in the open air, and on foot if possible. Since the morning stars first sang together, the whole creation has been groaning and travailing in preparing the earth for the habitation of man; and the influence and teachings of Nature have ever aided powerfully in perfecting man and upbuilding the ruling nations of the world. The progenitors of every vigorous race have always found in forest and wilderness the tonics and sources of their strength. It took forty years of wandering in the wilderness to prepare the Israelites for the occupation of the promised land. In the open and out-door life of the Athenians was developed a civilization noble in high aspirations for the ideal in beauty and life, rich in literary and oratorical achievements, and glorious in the great and profound thoughts of immortal teachers and philosophers. The august and all-conquering civilization of the Romans had its origin on Palatine Hill when herdsmen and wolves roamed over it. In Holland, where the people are ever in conflict with the elements of Nature, the land has been reclaimed by human effort from "the multitudinous waves of the sea." The streams that once spread over the land or hid themselves in quicksands and thickets are made to flow in channels and form a network of watery highways for commerce and the fertilization of the soil; and where formerly lagoons and morasses found a home, there are now pleasant homesteads, great cities, and beautiful villages. The Anglo-Saxon race, which is now and has been for centuries the most vigorous and progressive in the world, has always had an insatiable hunger for the earth, and a love for a life in the fields by stream or by roadside. Everywhere we find the highest type of civilization where man has gained the mastery of Nature by the work of his hands. The home of such a civilization is usually found where forests have been removed, and the wild vegetation of primitive times has been expelled to make room for the thousand and one productions of modern cultivation; where hillsides and mountain-cliffs have been festooned with vines and made to blossom like the rose; where watercourses have been made highways for trade and utilized for purposes of manufacture; and where gloomy morasses and damp lowlands have been dried up and made fertile and habitable by drainage and cultivation.