186 ARCHITECTURE. 
division, the building was to end, and a double portico of 10 and 4 
columns was added. This plan was accepted as unalterable by an apostolic 
brief. Lorenzetto served as superintendent under Michael Angelo, who 
conducted the work for seventeen years without remuneration. In the 
year 1557 Michael Angelo had completed the great vaults under the drum 
which was to bear the dome, and made the model of the dome, but this 
was not begun until twenty-four years after his death, which occurred the 
15th February, 1564. Pirro Ligorio succeeded Michael Angelo, but he 
did little, and Vignolo followed, with strict orders not to deviate a hair’s 
breadth from the plans of Michael Angelo. By him are the two side domes 
(jig. 3), and he faced the exterior wall with ashlers. After Vignola’s death 
in 1573, Gregory XIII. intrusted the work to Giacomo della Porta, who 
completed the building to the above-mentioned limits of Michael Angelo’s 
plan, after which only the dome, but that the most difficult part of all, 
remained to be executed. Sixtus V. now named the Chevalier Domenico 
_ Fontana as architect, whose son Carlo Fontana designed the centring. 
It consisted of eight suspension pieces uniting in the centre, and of beams 
jointed one above the other, over which the sixteen chief ribs of the vault 
were to be constructed simultaneously, all being kept at equal heights. 
On the 15th July, 1588, the work commenced with 600 laborers working in 
turns day and night, under the superintendence of Domenico Fontana, and 
twenty-two months later, on the 14th March, 1590, the pope himself laid 
the last consecrated stone in this vault. 
Meanwhile some fissures showed themselves in the vault of the dome, 
and its fall was feared. But Carlo Fontana showed the baselessness of such 
fears, and a great counsel of architects and mathematicians that was 
summoned in 1742 on the strength of similar apprehensions, decided that 
there was no reason to fear a fall, yet by Poleni’s advice it was coneluded 
for greater safety to place five girdles around the dome. This was accom- 
plished in 1747 by Vanvitelli, and since then no new precautions for security 
have been necessary. To return to the earlier history, the crypt under the 
middle of the church, to which access is had from the interior, was enlarged 
by Domenico Fontana, who also introduced additional light. 
As Michael Angelo’s plan ended at the point indicated above, and as it 
was feared that the interior might be too small for the immense throng that 
would assemble for the Year of Jubilee and the coronation of the Pope, 
Paul V. resolved to enlarge it. Maderno accomplished this by designing 
the remainder of the edifice including the portal of travertine. The five doors 
leading into the church are covered with bronze plates with costly bas-relieis. 
The middle one, with representations from the lives of the apostles Peter 
and Paul, was cast in 1430 by Antonio Filareto for the old church. The 
fifth door is walled up and is called the holy, because it is only opened once 
every year of jubilee. 
Until the year 1660 the church had no adequate avenue, and among 
many new and old plans Pope Alexander VII. chose the colonnade of 
Bernini shown in our ground plan (jig. 1). In order to complete it, it was 
necessary to remove many buildings, and among them the house of Raphael, 
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