Popular Science Monthly/Volume 21/July 1882/The Development of Cities
By M. BADOUREAU.
THE rectangular system of laying out streets has the advantage of extreme simplicity, and lends itself to a convenient adjustment of the interior of the houses of a city; but it is monotonous in the extreme, and makes communication between one quarter of the town and another very inconvenient; for the passenger is compelled to go along the two sides of a triangle to accomplish the distance represented by its hypotenuse. We have endeavored to solve the problem of the best way of arranging the streets of cities by mathematical calculations, but have found the task one leading to geometrical complications. We recommend the study to geometricians as an interesting one, and content ourselves here with stating the conclusions we have reached. We have examined the question in the two forms: By what law can we arrange the streets so as to lose the least possible amount of space, and still have the greatest possible length of roads; and, given a surface of which the shape and area are known, and the law of the division of the population having been ascertained, how shall we lay out the roads so as to make the different lines of communication, particularly the most frequented ones, as short as possible? Four plans ordinarily present themselves under which the ground selected for our city to be built on may be laid out: the square, hexagonal, octagonal, and circular. Of these, the hexagonal type seems, according to our mathematical calculations, the one which gives the greatest length of streets and the greatest amount of habitable surface, with the smallest consumption of space. As a rule, for cities the population of which is homogeneous, the octagonal and hexagonal plans are much preferable to the square in respect both to the utilization of the surface and the facility of communications. Unfortunately, both plans are liable to the objection that they give house-lots having acute angles of sixty degrees in the hexagonal, and of forty-five degrees in the octagonal plan. Practically the population finds it convenient to bear toward the center of the city, and, the more it bears that way, the more it is to its interest to do so. Consequently, the density of the population diminishes from the center toward the circumference. Under such conditions, the circular plan is very satisfactory. It has in effect the double advantage of furnishing direct roads to the center of the town, and of accommodating itself to giving to the houses in the outlying quarters the greater amount of space they require. For the center of cities, where the population is compact and homogeneous, where land is dear and communication is needed in every direction alike, the hexagonal plan, with the reservation of a few places for public monuments, is most convenient. This central part might be surrounded by a boulevard, beyond which the circular type might be adopted with modifications so as to avoid curved streets. The principal streets of each suburb might be directed toward the center of the city, and each suburb might in itself be laid out more or less according to the rectangular type. The transverse streets would, however, spread farther apart as the distance from the center became greater; and main diagonal streets might be arranged to cross the whole city, with few or only slight deviations. Beyond the suburbs, the principal radial streets might be continued for a considerable distance farther, but the transverse streets would nearly disappear. The accompanying design has been drawn according to these principles. It is worthy of remark that the sketch is more like the European cities that have grown up by progressive additions than the American cities which have been built on a so-called rational plan.
So far we have considered the question from an exclusively geometrical point of view. We may continue our study by referring to the influences which geographical, meteorological, commercial, and political conditions have had in the laying out of cities. Certain directions in the ways of communication are often imposed by the topographical situation; as, for example, when the town is crossed by a river or a highway. Some cities are free to extend over the plain in any direction, while others are restricted to narrow valleys, or to islands of which they cover the whole. The city of Cadiz, confined upon an island, has very high houses, with terraces and lookouts, the object being to reach a height where the air will be healthy and the rain-water pure. St. Malo is built much after the same fashion, and the
streets in both cities are very narrow. Every one knows that the principal highways in Venice are canals, and that the several islands are traversed by prodigiously narrow and crooked streets. On the other hand, the cities of Hungary extend over considerable spaces and are thinly populated. The city of Maria Theresa, or Szabadka, for instance, according to E. Keclus, covers a space of eight hundred and ninety-six square kilometres, and is really nothing but a province cut up by regular avenues, by the side of which houses stand at intervals—an oasis of stone in the immense plain.
We may remark, with respect to the bearing of climate, that narrow and crooked streets protect the inhabitants against heat and against cold, but they foster the accumulation of miasms and prevent the circulation of air. Cities tend to expand on the side from which the prevailing winds come. x It is the most pleasant side, because it is free from the unhealthy emanations of the town.
In considering the economical side, account must be taken of the density of the population and the frequency of communications. It is important that the principal centers be connected by wide, direct, and easy roads following the course of the most usual commercial currents. Theoretically, the width of each street should be proportionate to the traffic upon it.
Historical considerations may sometimes rule, for due force must be allowed to existing conditions in the construction of each new street.
Sometimes cities are built so fast that we might say they are made up of sections constructed after a plan framed in advance. In such cases they generally present a regular disposition. Such a town is Carlsruhe, in Baden, where the avenues converge toward the Château, and of such character are most American cities. Generally, however, in old Europe, cities develop themselves slowly, and the laying out of their streets has been influenced by the circumstances in their history.
Open cities generally expand gradually by the building of houses along the roads toward neighboring towns. They thus take a kind of radiated or palmate form, quite favorable to facility of communication.
Fortified cities are developed in an intermittent way. After having been for a long time smothered within their walls, they end by breaking the barriers down and uniting with their suburbs; constructing elegant boulevards in the places formerly occupied by their fortifications. The city of Paris bears the marks of several changes of this kind. Generally the extension takes place alike in all directions, and the towns that have undergone such metamorphoses present a succession of concentric zones separated by circular boulevards. The central nucleus generally offers a close agglomeration of high houses parted by narrow, crooked, and everywhere crowded streets. Here public and private business is transacted, and the centers of trade and amusement, the public offices, and the churches, are established. Through this part also lie the usual ways of passage from one suburb to another. Most frequently the old town is traversed by a grand artery, the history of which goes back to the origin of the place, and which is usually busy with trade and much crowded. The population of the suburbs is generally less dense than that of the city proper; and the streets are wider, and the houses farther apart. The inhabitants of the suburbs are in the habit of going frequently to the center of the city, because it is the most populous part, and because the roads to the other suburbs lie through it. The principal streets of the suburbs also converge toward the center.
All the characteristics we have sketched may be found in the city of Vienna, where the ancient city, still called die Stadt—"the City," rests on a branch of the Danube in the north, and on the Wien in the southwest. The cathedral, situated in the center of the town, St. Stephen's Place, and the Graben, are still the points toward which the Viennese and strangers are most in the habit of resorting; thence bear toward the north and toward the south, the Kärntnerstrasse and the Porte Rouge Street, so as to form a grand artery traversing the whole of the ancient city. One of the finest boulevards in the world has been built on the site of the fortifications that surrounded the place in the east, south, and west; and beyond this "Ring," as well as on the north side of the branch of the Danube, vast suburbs, regularly laid out, extend in every direction, enlarging tenfold the surface of the city.
Sometimes circumstances prevent the development being equal in every direction. The city of Antwerp, resting on the Scheldt, presents, with the suburbs that have recently been annexed to it, a semi-circular form. Calais has only one suburb, much more populous, it is true, than the city itself; and the fortifications which separate the town and its suburb are to be razed and replaced by boulevards. Dismantling is not the only agency by which the aspect of cities may be suddenly modified. A great fire, for example, destroyed the central part of the city of Rennes in 1720, after which a new town, with high houses, wide, straightened, and rectangular streets, and handsome squares, was built in place of the burned one. A few old quarters, which the fire had spared, formed an ugly enough inclosure for this new town, which still partly exists. At the same time the suburbs have stretched out along all the principal roads, and a few new quarters have been built in the healthiest part of the suburban zone. At other times the hand of man destroys entire quarters, to reconstruct them in a more convenient and more hygienic manner. In such cases the worst quarters are the first to suffer transformation, and become in their turn the most elegant ones. The example set in Paris, under the administration of M. Haussmann, has been extensively followed in other cities in France and abroad. The construction of new basins in sea-ports also frequently leads to radical modifications of the aspect of the towns and in the grouping of their streets. We are evidently very far from exhausting the questions that grow out of the subject; but we hope we have succeeded in showing how complex and interesting they are, and how imperfect is the plan of those cities that are laid out in a network of rectangular streets.—Translated from the Revue Scientifique.