precarious existence. Drainage, more and more extensively carried out, and the advance of hygienic science have modified and are still modifying these natural conditions; and the advance of civilization tends to diminish the difference in the specific value of climates to man.
As to the situation, man formerly, with his limited means, accommodated himself to Nature in the ways it offered. On the sea, he did not go far from the shores along which he coasted. On the land, he followed the stream, the valley, the mountain gorge, or the cove; and if the mountain stretched out in too compact a mass or presented a too high wall, rather than attack it in front he went round it. It is no longer so. Scientific advance has freed him from his close dependence upon these circumstances. The discovery of the compass brought on the advent of long sea voyages, and made possible the crossing of wide oceans. Moreover, we dig through continents to give passage to ships; attach islands to the mainland by means of gigantic viaducts; and pierce mountains by tunnels to give passage to railways. With each isthmus penetrated, each tunnel opened, and each new canal and railroad the courses of great commercial currents are turned. The road frequented yesterday is deserted to-day, and solitudes, lately unexplored, are filled with the periodical tumult of railway trains. Countries which were boasting of their situation deplore it now, as shops on a former principal thoroughfare in cities undergoing transformation are compelled to witness the diversion of movement and life away from them to new streets.
Thus the rational study of the soil as related to the successive scientific, historical, and social conditions of man gives the key to the local shiftings of civilization through the ages. It rested for a long time on the Mediterranean Sea, the peculiar situation and figure of which facilitated communication between bordering and adjacent countries, and this region was then the whole world, the sailor fancying when he got upon the ocean that he had passed the ends of the earth. The compass was discovered, sailors went farther, even to America, and the Atlantic Ocean became the center of the world; preponderance passed from the southern to the western countries of Europe. The development of steam navigation put all parts of the earth in constant communication. The Isthmus of Suez was pierced, and the Mediterranean recovered part of its lost prestige, while the Southern Atlantic ceased to be the principal route to the East Indies. Other changes, affecting the nations of western Europe, are still going on as results of these events; while in the extreme East, China, Japan, the Indies, and Australia, which were hardly known two hundred years ago, are forced into the current
