1846.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



97 



ON THE ENTASIS AND OTHER CURVED LINES OF THE 

 PARTHENON.* 



By F. Penrose, M.A., Magd. Coll., Cambridge, Associate of the 

 Institute. 



Read at the Rayal Institute of British Architects. 



{With an Engraving, Plate V.) 



It is an admirable principle of this Institution that it has for its object 

 the bringing together of various points of information from its different 

 members, inasmuch as no one can see or understand everything. It would 

 be contrary to the spirit of this proposition, to eipect that no one should get 

 op here to speak who had not materials for an entire evening's lecture. In 

 accordance with these views I shall only detain you a short time, to inform 

 jou of the results which I have arrived at, in a limited survey of the Par- 

 thenon ; all the measurements I took having reference to its scientific, not 

 its decorative construction. 



It is a very convenient season for such discussion, after the very edifying 

 and agreeable evening which we passed here on the last occasion of our 

 meeting, when the zeal of Mr. Lucas and the remarks which he called 

 forth from Mr. Donaldson, brought the subject so vividly into discussion. 



However I will proceed at once to what I have to say — The first point 

 to be considered is the carvature of the steps — it is obvious that the earlier 

 investigators of the Parthenon had no opportunity of observing this as the 

 ground was covered with rubbish, and it is so slight as to elude the eye 

 unless brought down to the level of it. 



Had Vitruvius however been in credit, the following passage would have 

 Bnfficed to suggest it, " The stylobate or step should be so set out as to 

 have in the middle an addition by means of unequal/oofsfoo/s (literally), 

 t. e. unequal blocks. For if it be made level, it will appear to the eye 

 Bunk in the middle (literally channelled) to the eye." Again, " When the 

 capitals are finished they must be arranged on the shafts of the columns. 

 Dot level, but according to the same measurement as before, so that the 

 symmetry of the architraves and upper members may correspond to the 

 same addition as was made in the stylobate," 



This was first observed in the Parthenon, I understand, by Mr. John 

 Pennethorne. He unfortunately, however, allowed the Germans to have 

 the credit of prior publication ; it made its appearance in a Vienna archi- 

 tectural journal, four years ago. I have a drawing (see plate), made from 

 my observations of the east front of the Parthenon. I levelled it, I believe, 

 very correctly, as my instrument, on being taken to the opposite end, gave 

 exactly the same line. I have drawn a black line along what I suppose 

 to have been the original line ; the shaded line marks that which I obtained 

 from my measurements ; these, in which I was assisted by Mr. G. Ken- 

 nedy, were taken with the French metre, and I have reduced them to 

 English feet and decimals of a foot, which, I think, is the best system we 

 can use for scientific mensuration — it were much to be wished that it 

 should become universal. A circumstance which would render this change 

 less troublesome to workmen is, that the 100th of a foot is nearly the same 

 as the eighth of an inch. 



Now, observing that the sixth column from south-east angle is the highest 

 for its situation of all the columns, and that the architrave above has a 

 crack about -06 feet in width, I infer that that point has been set most 

 firmly in the foundation, and the rest have all settled more or less about it. 

 This may perhaps have been all the result of earthquakes, as I found that 

 the base of the central columns of the west front were -08 feet higher than 

 those at the east end, and the base of the south angle column of west 

 front was -09 feet higher than that at its north angle. 



In the east front it will be seen by the drawing 4hat the north-east angle 

 of upper step is -028 feet lower than south-east angle, showing a settle- 

 ment in that part of the building, which is also attested by the aforesaid 

 eiack over the architrave of the sixth column. It will be seen that on the 

 south half of the front the step runs very nearly straight, except that at 

 the angular column there is a little more shoot, probably to throw off the 

 ■water better. And the angular column is about -02 feet longer than the 

 others to compensate for this. The step, at this point, has a gradient of 

 about f^, afterwards ^ nearly. The chief rise is -022 feet, which is about 

 the same as the amount which the columns lean from the perpendicular. 



• The curvature of the itvlobate of the Parthenon It briefly noticed In the Seventb 

 Volume of this Jouroal, p. 16. 



No. 103.— Vol. IX.— Apbu, 1846. 



The height above level of fourth column from the cast on the south flank is 

 •23. It is quite clear that the step has been lowered a trifle by settlement, 

 as the stones of the step immediately under the columns adhere so closely 

 that they have actually grown together, as Stuart found to be the case; 

 but lower down the joint is apparent enough. 



An hyperbola may be drawn approximating very nearly with the line 

 after allowing a very little for these settlements, which have unquestionably 

 taken place, and as the conic sections have been applied constantly in the 

 construction of this and the other temples at Athens, I think it not im- 

 probable that they were regulated in this matter by that curve. 



Can any geometrical or optical considerations suggest the ntcessity for 

 this addition in the middle of the stepf 



Vitruvius does not go so deep into this as he usually does on optical 

 questions ; he merely says that the step if level will look channelled. It 

 occurs to me that it is in the pediment and not in the step that we are to 

 look for the necessity of this correction. 



It is a matter of constant experience that the presence of a curved line 

 distorts any right line in its vicinity, as for instance, the tangent to a circle 

 always looks bent contrary to the curvature of the circle, and the same 

 thing is no less true of the chord. A small segment of a large circle may 

 be made to look straight, or even bent contrary to its real direction, by the 

 juxta-position of a curve of greater curvature. 



The same thing obtains more or less in a pediment where the converging 

 lines have ultimately exactly the same relative position as an arc and its 

 chord. And any portico to which these corrections are not applied will 

 give something of this feeling, if we look attentively at its angles. 

 Another confirmation of this view of the matter is, that in the great temple 

 at Paestum, (undoubtedly built some time before the temple of Theseus, )tlie 

 addition to the stylobate and entablature is applied only at the ends; the 

 flanks are horizontal. At Segeste, whose greatness is probably posterior 

 to the glorious days of Athens — and consequently their temple is to be 

 referred to a later period — the addition is on all sides as at the temples of 

 Athens. This adjustment could only be required in temples seen directly 

 opposite. So in the Propyloea, we do not find any addition made to the 

 stylobate. 



We have heard something of a curvature of the entablature in an 

 horizontal plane as well as the vertical. Mr Lucas stated last meeting 

 that he understood from Mr. Pennethorne that such was the case. I 

 admit that both the fronts of the Parthenon are bent inwards, but not that 

 it was so originally. 



In the east front of the Parthenon Ihe four first architrave stones are in a 

 continuous plane nearly vertical ; the fourth is bent slightly inwards away 

 from this, the rest are quite irregular. The entire deflexion in the east front 

 is not more than -09 feet. 



I observed that the joints of masonry on the fronts are almost all 

 crus'hed, so that it is clear that there has been a slight disturbance of the 

 original plane of the building ; indeed, the angular columns give less 

 declination than the central ones. 



I found that the fourth column from the south-east angle leant '235 feet ; 

 (this is the same as that given in the supplement to Stuart.) From the 

 north-east angular one I deduce '225 after allowing for the amount of set- 

 tlement due to the crack above the sixth column. I cannot admit that 

 such horizontal curvature was ever intended. Vitruvius does not mention 

 it, nor can any reason be assigned that I am aware of for the use of it. 

 Constructive and optical advantages are obtained both by tlie leaning of 

 the columns and the raising the stylobate and epistyle. It is evident that, 

 in a country liable to earthquakes, a certain degree of pyramidal construc- 

 tion given to the building must be of statical advantage. The slight dis- 

 turbance which has actually taken place has thrown the north-east angle 

 column about '07 feet to the right hand, and it would have leant away 

 from the building in an unsightly manner had not there been an original 

 declination three times as great inwards. 



Still I do not compare my argument a priori with that drawn from marks 

 of crushing and settlement on the building. As Wilkins fell into a sad 

 mistake when commentating on these very subjects in Vitruvius, when he 

 states his belief that it was only a fancy of Vitruvius, and did not enter 

 into the works of the ancients. Vitruvius is very positive about the lean- 

 ing of the columns, and states that their inner face should be parallel with 

 the wall of the cella. The columns of the Parthenon have not nearly eo 

 much lean as this, however owing to the nature of the curve of their 



13 



