The Day the Universe Changed - James Burke [37]
The first and most perfect example of Alberti’s rules and of the effect of Brunelleschi’s discovery of perspective is the church of S. Maria delle Carceri in Prato, a few miles from Florence. Probably designed by Alberti, it was begun by Giuliano da Sangallo in 1485. This centre-plan church introduced the form of the Greek cross. In the medieval world the cross had signified Christ crucified. Here the classical cross was used to give a sense of mathematical purity. Where Gothic had led mysteriously to the high altar and the towering spire above it, this new church invited rational evaluation. The exterior of S. Maria is formed of limestone slabs, divided into geometric units by green framing bands. The joints of the building are marked in pietra serena, grey stone, while the rest is white. Under the dome one stands at the centre of the church, and all around is harmony and proportion. It was this exact use of balance that showed the influence of perspective. Proportion was all. Alberti gave exact specifications for all churches. The height of the wall up to the vaulting should be half, two-thirds or three-quarters of the diameter of the plan. These proportions, of 1:2, 2:3 and 3:4, should dominate the structure. At S. Maria the four arms of the cross are equal in length. The depth of the arms is half their length. The four end walls are as long as they are high.
The church of S. Maria delle Carceri in Prato.
Alberti’s façade of S. Maria Novella, Florence, finished in 1470. The medieval bell-tower of the church can be seen in the background. The scrollwork on either side of the upper storey was the first move towards the florid, baroque style of the next century.
The use of proportion is best seen in Alberti’s design for the façade of S. Maria Novella in Florence. The new front was added to a Gothic church. Alberti obeyed his own injunctions. The front is a square, and the upper and lower storeys divide it in half. The upper storey of the facade is precisely half the total upper storey of the church. The lower storey is symmetrical about each half of the lower rectangle. The upper central bay, half the total upper area, is exactly split above and below the entablature. Half of this is equal to the width of the upper side bays. Up to this point everything is in the ratio 2:1. But the height of the entrance bay is one and a half times the width. So the width to height ratio is 2:3. The dark, square encrustations of the attic are one-third the height of the attic and relate to the column diameters in the ratio 2:1. The entire facade is geometrically built up in a progressive halving of ratios. It is the first great example of Renaissance eurhythmia, proportion.
The rules for the building of cities were equally concerned with proportion. Cities were to be the mirror of a harmonious universe, with buildings arranged according to function. These would be of three types: public buildings, for the princes; buildings for the wise, experienced, wealthy citizens, like Alberti’s Palazzo Rucellai in Florence; and decently constructed buildings for the poor. Throughout the city plans, man was the standard.
At the village of Corsignano, in Tuscany, the birthplace of the humanist Pope Pius II, the Pontiff ordered a town to be built according to the new rules, to be called Pienza. The architect was Bernardo Rossellino, who, among other things, asked that anybody who painted or in any way adorned the inside walls of the cathedral should be punished. The little town of Pienza still stands virtually as it was built, according to Alberti’s rules