Pennethorne, John; Robinson, John [Ill.]: The geometry and optics of ancient architecture: illustrated by examples from Thebes, Athens, and Rome (London [u.a.], 1878)

iv PREFACE.

" the Columns; also, to observe the mathematical knowledge exemplified by
" the Greeks in the forms of the Mouldings, and especially in the hyperbolic
" entasis of the Columns." For this purpose Mr. Penrose employed instru-
ments of a more delicate nature than are generally used for admeasure-
ments in Architecture, and nothing can exceed the scientific accuracy of
all his observations.

With regard to the curvature of the horizontal lines and to the
entasis of the Columns, the dimensions taken by Mr. Penrose supersede all
those previously obtained, for he has certainly proved by measurement that
all the horizontal lines are very correct arcs of circles, and that the entasis
of each Column is the true arc of a hyperbola. All his general measure-
ments are more to be trusted than any previously made: I have, therefore,
in the following work adopted them whenever I have been able to do so,
in preference either to my own or to those in Stuart and Eevett's valuable
work, " The Antiquities of Athens," published in 1762.

Also, without Mr. Penrose's general plan of the Acropolis, on which
the levels of the original roads and platforms below the Upper Step of
the Parthenon are carefully noted, I could not have made my calculations
with any degree of certainty.

For the profiles of the Capitals, and of the Mouldings and smaller
curves, I have used either accurate casts taken in wax, or the forms traced
upon paper direct from the marble, in preference to measurements, however
carefully made. The work of Mons. Beule, "L'Acropole dAthenes,"
published in 1862, is a valuable addition to our knowledge of the original
plan of the Acropolis, particularly with regard to the Propytea, and to
the plan of the marble staircase of approach to the central Portico.