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Francis Penrose

The main purpose of Stuart and Revett had been that of determining by which system of proportions the Parthenon had been calculated. The assumption, based on the Italian Renaissance tradition, diffused in England by Isaac Ware’s translation of Andrea Palladio, was that this system of proportions would reveal the secret of the beauty of the Parthenon and the secret of the beauty of Greek architecture in general. Since it was found impossible to reckon the proportions of the Parthenon by the Attic foot, one began to speak of the ”secret” of the Parthenon and to search for a mysterious ”key” that would unlock the recipe of Grecian esthetic perfection.

It was under the impulsion of this concern with the ”secret” of Greek architectural proportions that the architect Francis Penrose (b. 1817), all imbued with the Palladian tradition, dedicated a great part of his life energy (from 1845 to his death in 1903) to the measurement of the Parthenon. Fortunately, he had a truly scientific mind that made him separate facts from theory. In the first paragraph of the preface to the first edition of his monumental work, An Introduction to the Principles of Athenian Architecture (1888), he states that ”it professes simply to be a faithful record of observations made on the spot”—and he remained rigidly faithful to this declaration. Since he had received advanced training in mathematics and was an outstanding amateur astronomer, he well understood the technical requirements of the operations of measurement.1 He proceeded with a diligence quite unusual among archeologists, because he had inferred from the neatness of the joints of the stones of the Parthenon that the builders had aimed at extreme accuracy and precision.2

Penrose declares that his survey had two aims in mind. The first was to determine which standard of length had been employed by the builders. Once this first aim had been achieved it would be possible to reconstruct the system of proportions followed by the architects. He assumed that if the second aim could be achieved, one would have a cue for the understanding of the architecture of Greek temples in general. However, Penrose did not achieve his first aim and, hence, missed the second.

For the dimensions of the stylobate Stuart and Revett had concluded that the length exceeds 9/4 of the width by less than ½ of an English inch, or 6.35 mm. Penrose arrived at the following findings:

Table I: The Dimensions of the Stylobate according to Penrose

English feet


East side



West side



South side



North side



For the width Penrose based himself on the dimensions of the east side, which is better preserved, but deducted .006 feet (1.829 mm) to compensate for the coming apart of the blocks at the joints, arriving at a figure of 101,335 English feet (30.886.9 mm). In relation to the south side, Penrose found an excess of 124 feet (37.7 mm) by his uncorrected figure and of 137 feet (41.8 mm) by his corrected figure.3

On the basis of these results Penrose concluded that the Parthenon had not been calculated by Attic feet.4 He assumed that the Parthenon had been calculated in Roman feet and that it was merely a matter of establishing the exact value of this unit. The reason for which he proceeded from this assumption was that Böckh, in his epoch-making treatise on ancient metrology, published in 1838, had shown that the system of weights and measures established in Athens by Solon was based on the cube of the Roman foot. Scholars expected that the foot used as the basis of the official system of weights and measures would be the one used by architects. At the time the assumption that the buildings of classical Athens had been calculated by the legal standard of length was a reasonable one, since all Roman buildings of the late Republic and the Empire appear calculated by the Roman foot which is also the basis of the Roman system of volumes and weights.5 In reality, one cannot say that this is a generally-applicable principle. In Mesopotamia the units of weight and volume were reckoned by barley cubits (either natural or trimmed), but there are buildings calculated by other standards. In Egypt most buildings are usually calculated by the Egyptian royal foot, which is a multiple of the Egyptian foot used in setting up the basic standards of weight and volume, but other units of length were used as well.

In any case, whatever may have been the practice in other lands, it is a fact that Greek architects used whichever module of foot was more convenient. This procedure most likely reflects a particularly Greek concern with proportions. Having decided on the general dimensions of a building, Greek architects chose the module that could express more simply the system of proportions within the limits of the intended dimensions.6

Having decided that the Parthenon was calculated in Roman feet, Penrose had to reject the conclusion of Stuart and Revett, who understood the ancient literary texts as meaning that the width of the stylobate of the Parthenon was 100 feet. He went searching for a unit of 100 Roman feet that could have caused this temple to be called hekatompedos. At this point he paid attention to the fact that, although Greek literary texts give the name of hekatompedos neos to the Parthenon as a whole, there are Athenian inscriptions (published by Böckh) that use the term hekatompedos neos in referring specifically to the part of the temple in which there was kept the image of the Goddess, the famous chryselephantine statue cut by Pheidias. The Greek term neos may refer to a ”temple” in general, but more technically it refers to the ”shrine” where the image of the divinity is preserved. Hence, there cannot be any doubt that the part of the Parthenon which one would call ”the holy of holies” was hekatompedos. Penrose hit on the right solution of the problem, but he did not apply it correctly, because he failed in identifying this inner temple.

For reasons that I shall explain, the cella of the Parthenon is divided in a manner most unusual for Greek temples. It is divided by a wall without openings into two completely separate rooms. The west room was the parthenon in the technical sense of the term, ”the sleeping place of the Maiden.” It is an approximately square room that occupies about one third of the cella. The east part of the cella, on the other side of the partition wall, was a rectangular room that was subdivided by a colonnade that enclosed on three sides the statue of the Goddess. This colonnade was so built that all around it there remained a relatively narrow corridor, running between the colonnade and the two outside walls of the cella and the separation wall that delimits the Parthenon in the narrow sense of the term. It was the colonnade that marked the area that was called neos in the strict sense of the term, ”the shrine of the image.” The isolation of the area enclosed by the colonnade was further enhanced by a grating that closed the intervals between the columns. Today nothing remains of the east part of the cella except the floor and most of the stones that form the very first layer of the walls. The colonnade that surrounded the statue has completely disappeared, but one can visualize quite clearly the line that passed through the center of the columns. This rectangle is the most evident feature that meets the eye of an observer who muses over the ruins of the east part of the cella, while he bemoans the bull’s eye scored by a Venetian bomb which made such a clean sweep of the area.7 Penrose recognized the existence of this rectangle and proceeded to measure it with the greatest care. However, in order to give significance to the lateral walls of the east part of the cella, Penrose was driven to misinterpret the architectural interpretation of the neos. He saw the colonnade as dividing the east room into three aisles as in a Christian church. This explanation was perhaps justifiable in the first part of the last century, because there were still in place the remains of a Byzantine remodeling by which the cella of the Parthenon had been changed into a church with three aisles, removing the original columns and replacing them with two rows of smaller columns. But once the Byzantine additions were completely removed, it became clear that the three narrow corridors that run between the colonnade and the walls of the east part of the cella have nothing to do with aisles. It is unconscionable to continue to speak of aisles today. Penrose himself came close to the truth when he referred to them as ambulatory spaces.

In a sense, these corridors were a waste of space—being separated from the naos proper by the grating between the individual columns, they were not open to visitors. Some scholars have tried to explain their existence as light wells through which light was thrown from the sides into the area enclosed by the colonnade, with striking effects. It is possible that this hypothesis is correct, but since nothing above floor level remains of this part of the temple, there is no evidence by which it can be substantiated. But one has reasonable grounds for doubting the opposite hypothesis that the entire neos with the statue of the Maiden were in darkness, except for the little light that came through the door.

Penrose did not consider the fact that the colonnade of the Eastern Room had been removed by the Christians.8 Hence, he conceived the Eastern Room as being similar to the atrium of a Roman house: the colonnade would have supported a roof that covered the corridors outside the colonnade (peripteral spaces according to my interpretation), whereas the central area would have been uncovered. He reasoned that the floor enclosed by the colonnade was at a level lower than the surrounding corridors because it had to collect the rain that poured on it—at present it is lower by 20 mm. on the north side and by 40 mm. on the south side. Hence, he gave to this floor the name of impluvium. But against this conclusion of Penrose there was later objected that there is not any trace of the drainage canals that would have been necessary to drain the water from the alleged impluvium.

Having rejected Penrose’s view, today the prevailing opinion has swung to the opposite view that the Eastern Room received light only through the door. The main support of this theory is provided by the writers who, having seen the building before 1687 A.D., were struck by its inner darkness. Bernard Randolph reported: ”The temple is very dark, having only some lights to the eastwards”—that is, the two windows opened by the Christians in the eastern wall. Spon, after expressing his astonishment (étonné), tried to find a reason why the architect Iktinos would have built such a gloomy (sombre) temple.

It is not likely that the statue of Athena was placed inside a sort of cellar. One must remember that in the pagan Temple there was not only a problem of light, but also of ventilation, since in pre-Christian times the partition wall had no openings. Most decisive is the fact that Greek columns were conceived in their overall features and in their details in order to achieve specific plays with the rays of light: a colonnade of fluted Doric columns would have made no sense inside a dark room.

In my opinion a fundamental piece of information is contained in a report in which Francesco Morosini gives an account of his feat to the Doge of Venice. Morosini explains that it would have been pointless to drop bombs onto the roof of the Temple, because they could have gone through il pavimento superiore, which ”had been put together so as to achieve the most powerful staying power,” except that ”in some places” there were ”some domes the extremities of which were composed of bricks” through which a well-placed bomb could and did go through.

Next, we must consider two drawings that reveal that the central half of the roof was higher than the sections at the two ends. This means that light was intended to enter from the two sides of the higher section of the roof.

Another piece of relevant information is that the bomb that went through was fired by a batter of two mortars placed at the eastern foot of the Acropolis, which were shooting almost vertically, as mortars are intended to do. The battery of six cannons placed below the monument of Philopappos was not expected to achieve anything against the Temple with its more direct trajectory.

From these data it may be concluded that under the roof there was a solid horizontal floor of stone. In this floor, called pavimento by Morosini, however, there were openings, square or circular, which let go through the light that entered from the sides of the roof. The Christians apparently closed these openings with domes or vaults of bricks.

Next, we must ask what was supported by the columns of the neos, since they were removed without causing the collapse of the roof. I suggest that they supported a flat ceiling which formed a sort of baldaquin over the statue of Athena. If this supposition is true, the light that came in through the sides of the raised part of the roof and through the openings of the pavimento mentioned by Morosini, would have been bounced back to reach the neos through the sides of the colonnade. The ceiling supported by the columns of the neos not only prevented the light from coming in directly, but collected whatever rain would enter from the sides of the roof. The Christians, since they had removed this ceiling, closed the openings in the pavimento.

The mentioned drawings indicate that by the period in which the Temple was visited by Randolph, Babin, Spon and Wheeler, the section of the carpentry of the roof above the opisthodomos had collapsed. Since none of the visitors mentions this fact, it follows that the pavimento as sealed by the Christians was adequate to keep rain and light out. The tiled roof was a strict necessity only when there were light wells in the pavimento. According to my interpretation, the neos received light from the sides through the colonnade. In this way the indirect lighting of the neos and of the statue could be carefully planned, achieving striking effects.

If Penrose had measured the length of the colonnade from the outside line of the entrance door, he would have identified the hekatompedos neos. But Penrose, who in the hope of identifying the hekatompedos neos measured again and again this area in all directions, missed measuring this particular temple directly. He states that the east room is 98.145 English feet long, counting inside the walls, and that the corridor between the colonnade and the separation wall is 13.97 feet wide. Hence, adding the width of the east wall of the cella, which is 6.82 feet, we obtain:

98.145 feet

-13.97 feet

+ 6.82 feet

= 90.995 feet

29,915 mm  - 4,258 mm + 2,073 mm = 27,730 mm

From the report of Balanos we get these figures for the same intervals:

29,746 mm

- 4,339 mm

+ 2,090 mm

= 27,497 mm

The differences result from the fact that there are small sills at the foot of the walls which may or may not be included in the reckonings. Further, Balanos measured the length of the neos counting from the foot of the columns instead of counting from the line of the stylobate. In my opinion the stylobate of the colonnade forming the neos, counting from the external limit of the door, was planned to have a length of 100 trimmed lesser feet (27,745 mm.) Unfortunately one has tested practically everything on the Parthenon except this particular dimension.

Penrose was inclined to accept as a valid estimate of the Roman foot that of 16,50 English inches, or 295.9097 mm. Since he was looking for a dimension of some 29.6 m., or 100 Roman feet, when he found that the east room, measured at the inside of the walls, was 29,915 mm., he announced that the length that caused the neos to be called hekatompedos was that of the wall that closes the rectangle marked by the columns. Since the wall of the neos was excessive for 100 feet, he deducted the small sill at the foot of the walls, and arrived at 29,782 mm. This was still too much for 100 Roman feet. Hence, after scholars, having noticed that at the inside of the east wall of the east room there are two buttresses, one on each side, that protrude by 253 mm., this amount was deducted from the internal length of the east room, arriving at a figure of 29,662 mm., which more closely approaches to 100 Roman feet.

After the publication of the report of Penrose, scholars split into two factions: those who followed the interpretation of Stuart and Revett that the Parthenon was called hekatompedos because it measured 100 geographic feet on the width of the stylobate, and those who claimed that it was so called because it measured 100 Roman feet on the inside of the East Room. Whether one follows one interpretation or the other, the length of the Roman foot must be increased. Hence, on the basis of the dimensions of the Parthenon and in conflict with all other evidence, in metrological writings of the second half of the nineteenth century one finds estimates of the Roman foot that are by far excessive.9 Whether the Parthenon is measured in geographic feet or in Roman feet, it is not possible to express the dimensions of its several parts in round figures. Penrose, although believing that the Parthenon had been calculated in Roman feet, admitted with the scientific honesty that characterized him: ”but it is remarkable how seldom the foot or its sixteenth part, the dactyl, occur in integers throughout the Parthenon.” (p. 13)

Scholars, instead of concentrating on the interpretation of the data collected by Penrose, thought that there was something faulty with his data. Hence, the Parthenon has been measured again and again. Large sums were invested by learned societies to this purpose and a number of noted archeologists spent years of their lives measuring the stones of the Parthenon. All these surveys have added little to our knowledge, except in some details. Actually, most of these surveys added to the intellectual confusion because they were far less accurate in the operation of measurement than Penrose had been. When one compares item by item some of the much-bruited surveys, one is left wondering as to which methods were used. For instance, the survey conducted by the art historian Lucien Magne almost constantly arrives at a length that is too short. Hence, the matter of the dimensions of the Parthenon became progressively more confused. Figures have been quoted from one book to another with the attending effect of misprints, misquotations, rounding of figures and conversions back and forth between French metric units and English units. The confusion has become so great that in the highly respected text book on Greek architecture by Robertson, one can read that the inner amphiprostyle temple has a stylobate with the following dimensions:

East side

21.72 mm

West side

22.34 mm

North side

59.02 mm

South side 59.83 mm

In reality there is no appreciable difference between the opposite sides. These errors are not immaterial, since they are used to argue that the builders of the Parthenon and the Greeks in general were quite casual in matters of dimensions.


  1. Penrose undertook important tests only when the temperature of the air was between 10° and 11.9° Reamur (about 55° to 58° Fahrenheit). This means that he avoided measuring during the summer when in Greece there is a sharp difference of temperature between the shaded and sunlit places. He had his excellent reference rulers tested before leaving London and upon his return. In his first campaign he found that the rulers, which had been carefully protected from impacts, nevertheless had shrunk by 1/1000 of foot over 4 feet, merely because of the vibrations of transportation. He corrected his results accordingly.
  2. Having compared several surveys of the Parthenon item by item, I have come to the conclusion that that of Penrose is the most reliable. The only valuable addition to the report of Penrose is provided by the measurements performed by Nicolas Balanos, Curator of the Monuments of the Acropolis, for the purpose of proceeding to a restoration of the peripteral colonnade. It is regrettable that Balanos, who had an occasion to examine the blocks one by one, did not distinguish the data that are certain and those that are hypothetical.
  3. Unless the contrary is stated, the figures quoted in the following pages will be those of Penrose, converted into metric units from the foot of the Imperial Standard Yard (304.79974 mm) and rounded to the tenth of millimeter.
  4. More recent surveys arrive at the figure of 30,889 mm for the actual length of the east side. According to my reckoning, the theoretical width was 30,889.2 mm. Penrose did not take into account the wear of the blocks as the result of exposure to the weather for about two and a half millennia.
  5. I say appear, because exceptions may have been missed, since antiquarians and archeologists in examining Roman buildings have always presumed a reckoning by Roman feet. The matter of the Roman architectural standard should be re-examined, since there have been found several Roman bronze foot-rules that are graduated by modules other than the Roman foot, particularly by the Egyptian foot of 300 mm., which with carelessness can be mistaken for a Roman foot. Other units of length were certainly used in land surveying.
  6. An example of such an approach is provided by the Athenian figured vases. An immense amount of time and energy has been expended on the study of their dimensions without arriving at any result, simply because the specialists on Greek pottery have chosen to ignore completely the science of metrology. For instance, they never measure the volume, even though a vase is first of all a container, and all vases, even when they are not intended to be used as instruments of measurement, are planned for a given capacity. From what I have been able to determine Athenian producers of artistic vases chose with the greatest freedom the standard of length that was convenient for the desired size of the vase. One of the major dimensions, either the width or the height, is almost always a foot or a cubit, or, when unavoidable, because of the general size of the vase, a simple multiple or submultiple of the foot or cubit, but all possible modules of foot or cubit are used. There are some Athenian painted vases that can be traced to the same workshop or the same artist, which are identical in proportions but have been calculated by a different foot or cubit. The only real difficulty in the supposedly most abstruse topic of the dimensions of Attic figured vases is the modification of the original dimensions because of the shrinking of the clay in baking.
  7. Professor Jay Hambridge of Yale in his book which claims to unlock the key to the secret of the Parthenon, published a photograph of the cella seen from above in which this rectangle is traced over with a dark line; he recognized the prominence of this rectangle, even though it does not help him in defending his theory.
  8. Even after the transformation of the Parthenon into a Christian church the continuity of the cult of Athena was somehow maintained by consecrating this church to the cult of hagia sophia, or Holy Wisdom. When Constantine moved the capital of the empire to Byzantium, he had Pheidias’s chryselephantine statue of Athena brought from its old home inside the Parthenon to the new center of power, there to stand on top of a column in the Forum of Constantine, within sight of the great new temple of Hagia Sophia. The statue survived until 1203 A.D., when it was smashed to pieces during the siege of Constantinople by the Fourth Crusade. Cf. Nicetae Choniatae, Isaacius Angelus et Alexius F. in Migne, Patrologia Graeca, cl. 939-942 (1203 A.D.)
  9. Before the survey of Penrose, in the first half of the nineteenth century, one generally accepted as significant the estimate of the Roman foot made by Luigi Canina who was the first to use French units in testing the ruins of Rome. Canina had settled for the value of 296 mm., which is fair enough (it implies a Roman libra of 324.017920 grams instead of 324.0; 5002.766 English grains instead of 5000). From Canina’s figure for the Roman foot one could have derived a value of the Athenian drachma of classical times of 4.32237 grams (the correct figure being 4.320). But some later metrologists reasoned that, if the width of the Parthenon is 100 geographic feet of 308.87 mm., the Roman foot must be 296.51 mm. Others argued that from the length of the inside of the east room of the Parthenon it must be concluded that the Roman foot was about 296.70 mm. From this it was argued that the drachma was 4.3666 grams, and this figure is still repeated today by some numismatists, although it is in open conflict with numismatic evidence.

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