From the foregoing facts, M. Junod lays down the following directions: First, persons who are free to choose, especially those of delicate health, should reside in the western part of a city. Secondly, for the same reason, all the establishments that send forth vapors or injurious gases should be in the eastern part. Thirdly and finally, in erecting a house in the city, and even in the country, the kitchen should be on the eastern side, as well as all the out-houses from which unhealthy emanations might spread into the apartments. M. Elie de Beaumont has since mentioned some facts which tend to prove the constancy and generality of the rule laid down by M. Junod. He noticed in most of the large cities this tendency of the wealthy class to move to the same side--generally, the western--unless hindered by certain local obstacles. Turin, Liége, and Caen are examples of this. M. Moquin-Tandon has observed the same thing at Montpellier and at Toulouse. Paris and London also present analogous facts, although the rivers which traverse those two great centres flow in a diametrically different direction. Paris increased in a north-easterly direction at the time when the Bastille, the Palais des Tournelles, the Hotel St. Paul, etc., were built; but the inhabitants were then influenced by fear of the aggressive Normans, whose fleets ascended the Seine as far as Paris, and were only arrested by the Pont-au-Change. At that time, and as long as this fear lasted, they must have felt unwilling to live in Auteuil or Grenelle, But since the foundation of the Louvre, and especially since the reign of Henri Quatre, the current has resumed its normal direction. {80} M. Elie de Beaumont is inclined to believe that, among the causes of this phenomenon, we should reckon the temperature and the hygrometrical state of the air, which is generally warmer and more moist during the winds from the west and south-west than during the east and north-east winds. What most contributes to prolong existence is a certain uniformity in heat and cold, and in the density and rarity of the atmosphere. This is why the countries in which the barometer and thermometer are subject to sudden and considerable changes are never favorable to the duration of life. They may be healthy, and man may live a long time there; but he will never attain a very advanced age, because the variations of the atmosphere produce many interior changes which consume, to a surprising degree, both the strength and the organs of life.