Leaning Tower of Pisa
Cresy and Taylor
Elevation and Section - 1817
Rilievi di Cresy e Taylor (1817) riprodotti da Grassi (1831).
Elevation by Cresy and Taylor (1817), reproduced by Grassi (1831).
From http://www.endex.com/gf/buildings/ltpisa/ltpinfo/ltpgraphiche/ltpgraphice.htm:
In the year 1909 a Committee was appointed to study and record the static conditions of the Campanile and it was affirmed that the leaning had increased by 20 cm. (10.4 in.) since the last measurement were executed in 1817 by the English professors Cresy and Taylor.
BRIEF HISTORY of the TOWER of PISA
(Chapter 7 - How Much Does it Lean?)
by Piero Pierotti
Published by: PACINI Editore
Copyright 2003 Pacini Editore S.p.A.
ISBN 88-7781-481-0
This strange bell tower has always caught the fascination of strangers; perhaps by its own origin, having been thought of as a belvedere offered to the Mediterranean people, or perhaps for the singularity of being an a bell tower open toward the exterior.
In the middle of so many enclosed towers, impenetrable, hostile, this one with six circular loggias, from which one could be seen and call out to greet others as from a house balcony, arouses a sense of unusual familiarity and therefore of liking. Its deformity creates surprise but also stimulates a maternal sense, engendering a desire for protection, an obligation to try to do something. Finally, and undeniably, a phallic symbol, that has the attraction and the same appealing significance of many Indian temples. These archetypical feelings, universal, do not have geographic confinements - they cross over nationalisms. Therefore it is not exceptional that the first architectural measurements of the distinguished tower were taken by two Englishmen and a Frenchman.
Edward Cresy and George Ledwell Taylor measured and reproduced the piazza in every detail during their stay in Pisa in 1817. They anticipated the first visit of a their fellow countryman, the poet Percy Bysshe Shelley, who, on May 7 of the following year stayed at the Hotel of the Three Damsels, on the lung'Arno, and found the city very unpleasant, almost deprived of inhabitants.
He departed in a hurry but when he returned there, on 26 January 1820, he stopped to pass what was left of his brief life. There was no change in his notion of Pisa as a "desolation of a city, that was the cradle and is now the grave of an extinct people," as he wrote in that same year. This sense of loneliness and abandonment seized all the strangers who visited Pisa, at least on the first impression. But many stayed, perhaps precisely those who loved the contrast between a city almost dead and the visible remains of its previous glory.
Cresy and Taylor arrived in Pisa with the spirit of archeological explorers in search of ancient testimonies about this piazza, that raised an exclamation of white marble from the medieval Dark Ages, expressed in classical form.
They could certainly not repeat the enterprise of their fortunate countryman Lord Elgin, who had taken up the ruins of the Parthenon to carry it to London. They were satisfied therefore to document it, much more respectful, and with great deliberation, they set out to measure and to survey the monuments of the piazza.
They did not spare any critique of the bell tower, guilty of leaning in the face of such perfection of lines and of arcs. In Italy, they observed, the earth is mobile and special intelligence is usually applied to build a bell tower: "for example Buono, in 1148, appeared to use a great amount of qualified care to prepare and extend the foundations of the tower in front of San Marco in Venice, and it is quite odd that he would not take great precautions for that of Pisa, initiated almost 30 years later on a much worse foundation". They could not predict that 85 years later the bell tower of San Marco would be destroyed in a heap of dust.
But this observation of Cresy and Taylor was not dictated by any malice or animosity. Instead, finding themselves in front of a clear imperfection, they set their mind to calculate the absolute value and they were the first to leave a testimony defined with great precision. They conducted their survey two times, in two different way. They got values very close in both the measurements: 12 feet 6 thumbs and a quarter, 12 feet and 7 thumbs, "with a difference of only three quarters of a thumb from the first experiment."
The plane of reference to measure the lean is the cornice at the seventh level, that is the point of greatest projection of the construction. The measurements that the two Englishmen leave us are very precise and there are no means to doubt the correctness of their survey.
Certainly more vague is the data furnished by Giorgio Vasari toward the end of the 16th century (6 braccia and half), since he does not elaborate to us on which method and from where he measured. But Vasari was also an architect: his measurements were probably taken from the same points of reference used by the two Englishmen and, before them, by Giovanni Pisano, that is on the interior of the cylinder and on the outside of the seventh level. Therefore the surveys by Vasari and those of the English architects, are viable, taken with precautions suited to the conditions, and they can be considered comparable.
But the comparison is surprising. In fact the 6 and a half braccia of Vasari equates to 3.79 m, while the 12 feet and 7 thumbs of the English, calculated with the equal foot to 30.48 cm and the thumb equal to 2.54 cm, gives 3.84 m. If then it takes the second result of 12 feet and 7 thumbs the values are practically identical. That amounts to say that in practice, from 1550 to around 1817, the tower would have been almost static. Therefore it would have behaved as the three other leaning bell towers St. Michel in Borgo, St. Michele degli Scalzi and St. Nicola: after an initial period very sensitive to movement they found their point of definitive stability.
We could find a confirmation in one other exercise of small precedent, though it is not similarly verifiable: that of the architect Alessandro da Morrona, the most illustrious scholar among those who were concerned with the history of the Pisan monuments, he devoted a whole paragraph of his Pisa Illustrated to the matter of the inclination but stated two different values. When, however, Da Morrona measured the inclination on the inside of the cylinder he got a notable result: "... taking the exact measurement, the resulting inside slant of about six and a half braccia."
In conclusion we would have three values equal in intervals of almost three centuries: in 1550 (Vasari), in 1787 (Da Morrona), in 1817 (Cresy and Taylor). If we consider such values exact, we deduce that the tower had already stopped moving by the time of Vasari and perhaps before. If we only consider them approximately believable we reach the conclusion that the movement is so detectably small that there is essentially no difference.
Da Morrona demonstrates even better to be absolutely convinced of the immobility of the building, when he launches into praise of the presumed authors of the campanile (Bonanno and William of Innsbruck), who "constructed in that time the wonderful Tower, that was able to subsist without manifesting even the slightest lack of dignity to its Art and to the City, that justly displays its glories," The phrase is repeated, varying a few words, in the edition of Pisa Illustrated published in 1812, where the data is also confirmed at 6 braccia and half, then only five years away from the surveys conducted with such precision by his English colleagues.
However there is nothing made by an Englishman that a Frenchman would not propose to make better. So in 1859 a study of the bell tower is undertaken and in 1866 a rich harvest of surveys taken by George Rohault de Fleury who refers to a great number of medieval buildings and among these, once more, the leaning tower. Unfortunately we can not read an account on the reckoning of the inclination as precise as that left by Cresy and Taylor. For the measurement of the inclination we must base it directly on the sketches, on whose interpretation however there is dissent. The correctness of the surveys undertaken by Rohault de Fleury, and quoted with all the measures of the case, was placed into discussion by the committee of 1907, the first of the new century to deal with the problem. The increase of inclination recorded by Rohault de Fleury as regards the English, appear exaggerated, really frightening in such few years. Therefore taking into consideration two possibilities: either the Frenchman was not precise or something serious must have happened between 1817 and 1859. But what?
Toniolo Educational Centre, Museo dell'Opera, Opera della Primaziale Pisana
Torre.duomo.pisa.it
Leaning Tower of Pisa Articles
Leaning Tower of Pisa History
Leaning Tower of Pisa News
Leaning Tower of Pisa Web Links
Leaning Tower of Pisa Humor
Leaning Tower of Pisa Gallery
This page maintained by Gary Feuerstein
Posted: 5 Movember 2005