URBANISM — CLERGET. 659 



industries are established on the boundary and even outside the city. 

 Berlin has, in this way, developed industrial establishments directly 

 dependent upon that city covering a radius of 100 kilometers. There 

 is also a financial reason for this spreading out, and that is the decrease 

 in average location values from the center toward tlie boundary. 



III. URBANISM IN THE NINETEENTH CENTURY. 

 («) Geographical Situation. 



The formation of centers of po])ulation and of ways of communica- 

 tion which unite them is determined at once by conditions dependent 

 on man, based on the degree of culture and on political considerations 

 and by certain natural conditions, such as the richness and lay of the 

 land as well as to other factors connected with the climate.' The 

 influence of latitude is very marked. If you look at the annual 

 average isotherms on a map, you will see that the most important 

 city aggregations of the Northern Hemisphere are grouped chiefly 

 between the extreme limits of 16° C. (60° F.) (St. Louis, Lisbon, Genoa, 

 Rome, Constantinople, Shanghai, Osaka, Kioto, etc.), and 4° C. 

 (40° F.) (Quebec, Christiania, Stockholm, St. Petersburg, etc.). 

 The isotherm 10° C. (50° F.) represents accurately enough the central 

 axis of this zone, within which are found Chicago, New York, London, 

 Vienna,- etc. The Tropical Zone includes only 24 cities of more than 

 100,000 inhabitants, 15 of which are in Asia, 6 in America, 2 in 

 Oceanica, and 1 in Africa. 



High altitudes, like extreme temperatures, diminish populations, 

 which disappear completely at a certam limit. In Europe the inhab- 

 ited centers only exceptionally exceed an altitude of 1 ,500 meters (5,000 

 feet). But in the Tropical Zone it is natural that populations seek 

 high altitudes so as to profit by the lowering of the temperature and to 

 derive benefit from a temperate climate. In Abyssinia, the inhabited 

 zone is almost entirely included between 1,800 and 2,500 meters alti- 

 tude. Sana, in Arabia, is 2,150 meters high; Teheran (250,000 pop- 

 ulation) is at a height of 1,230 meters. In Tibet, Lassa is 3,560 

 meters high and Chigatzo 3,620 meters. From Mexico to Chile, aside 

 from some ports on the ocean, in nearly every instance you must seek 

 above 2,000 meters for the most important cities. IMexico City at 

 2,300 meters numbers more than 300,000 inhabitants; Quito, with 

 80,000 inhabitants, is 2,850 metei-s high; La Paz, with 63,000 inhabi- 

 tants, 2,700 meters; and Potosi, with 16,000 inhabitants, is at an 

 elevation of 4,000 meters ^ (13,000 feet). 



1 E. Cammaerts. J.-G. Kohl et la gfographie des communications. Bulletin de la Soci6t6 royale beige de 

 g&)graphie, 1904. 



- L. Metchnikoff, op. cit. 



2 Louis Gobet. Les grandes villas de la tcrre situ^es au-dessus de 2,000 m. Revue de Fribourg, 190.3, 

 p. 45-60. In Europe the great aggregations are all below 200 meters: Berlin, 25 m., Paris, 26 m., Vienna, 

 157 m., etc. 



