Perspective, to which several chapters are devoted, has to do with the methods of arranging real outlines and with them, of course, measurements, so as to have them pro-duce a certain desired visual result, whereas proportion has to do with the measurements as they appear in the result after perspective has produced it.
Proportion and Harmony of Line and Color, Preface.
Though in nature the measurements of an object may fulfil the requirements of proportion, they may not, owing to the operation of the laws of perspective, fulfil them in the image which this object produces on the retina; and, vice versa, though in nature the measurements may not fulfil the requirements of proportion, they may, nevertheless, owing to the operations of the laws of perspective, fulfil them in this image. In short, as applied to proportion as to many other artistic features, a work of art, whether a painting, a statue, or a building, has to be judged by what may be termed, and is, in this sense, its subjective effect after it has begun to influence the eye and mind.Idem. Iv.
But enough has now been said to verify the statement that the ancient architects in order to fulfil both visual and aesthetic, both physiological and psychical, requirements erected their buildings with primary reference to their general effects when seen from some definite point or points at a distance. In connection with this it has been shown also that these architects differed materially with reference to the particular methods through which to secure these effects, arriving at their conclusions, probably, as a result of many individual experiences and experiments.
Since the printing of the first edition of this book, Professor W. H. Goodyear has discovered that the methods attributed in this discussion to only the ancient Greeks, the Egyptians, and the Romans, were used also by the early Gothic architects. He himself has measured eighty-five of their churches in Italy which have floors rising between the front door and the chancel, sometimes, three feet, while, often, the successive key-stones of the arches between the nave and the aisles descend in the same direction,evidently to increase the effect of distance according to the laws of perspective. To what extent the same methods are exemplified in the Gothic churches of northern Europe, has not yet been determined.Idem, XV.