The drying up of a marsh, the cutting down of a forest, the substitution of one crop for another, may effect atmospheric changes through an extended radius, which will strengthen or weaken the vitality of the people. Some years since, there was a marsh behind the city of Cairo, which was separated from the desert by a hill. It was always noticed that the pestilential epidemics appeared to spring from that unhealthy spot and finally to spread throughout the east. The Pacha of Egypt, without thinking of this coincidence, noticed, on the other hand, that the hill behind the marsh entirely concealed the fine view which he would have from his palace, if it were removed. He gave orders to cut the hill down and to fill up the marsh with its _débris_, so that the winds which were formerly checked, had free circulation and purified the atmosphere, while the soil, thoroughly modified, ceased to emit the pestilential effluvia, Since that event the plague has not reappeared. A caprice of the Pacha effected more than all the quarantines and all the efforts of science, He has freed the world, perhaps for ever, from the most terrible of scourges. It is known that the cholera comes from India. It is engendered in the immense triangular space formed by two rivers: the Ganges and the Brahmapootra. It is the East India Company according to M. le Comte de Waren, that should be accused of treason to humanity. It is that power which has destroyed the canals and the derivations of the two finest rivers in the world. During the last twenty-five years of English occupation the number of pools in a single district, that of _Nort Arcoth_, which burst or were destroyed, amounted to eleven hundred. In the time of the Mogul conquerors, a fine canal, the Doab, extending from Delhi, fertilized two hundred leagues in its course. This canal is destroyed, and the lands, once so fertile and healthy, are now the infectious lair of wild beasts, having been depopulated by disease and death. {85} The hygienic condition of different countries, then, may be modified in various ways. In 1698, Bigot de Molville, president _à mortier_ of the Parliament of Normandy, found, after careful research, that, of all the cities of France, Rouen possessed the greatest number of octogenarians and centenarians. Toward the middle of the last century this superiority was claimed by Boulogne-sur-mer, which retained it for nearly fifty years, and was then called the _patrie des vieillards_.