THE ROSE WINDOW - A BRIEF DEFINITION

The Rose Window

        A circular window, with mullions and traceries generally radiating from the center, and filled with stained glasses. The term is suggested by the fancied resemblance of the window with its traceries to the rose and its petals. The rose window is one of the most beautiful and characteristic features of medieval architecture, especially of the French Gothic, in which it achieved its most perfect development. Its origin is to be found in the Roman oculus. During the Romanesque period the oculus became a window, and from about the middle of the twelfth century its dimensions began to increase with the development of gothic of Gothic architecture. By the middle of the thirteenth century it had attained the greatest possible size -- the entire width of the nave. Its splendour continued in France until the misfortunes of the later fourteenth and fifteenth centuries prevented the construction of large churches. The most beautiful examples of rose windows are to be found in the Ile de France and the adjoining provinces, Picardy and Champagne. The earliest important examples are the west rose of the Cathedral of Mantes (c. 1200); the west rose of Notre Dame of Paris (c. 1220), the most beautiful of all, and those of Laon and Chartres. In all these cases the rose was put under a circular arch. The next important step was to put it under a pointed arch, as was done in the beautiful rose windows of the Cathedral of Reims, 1230, as well in the transepts as in the later roses of the facade. Thereupon the rose was inscribed in square, with pierced spandrils as in the  transepts of Notre Dame of Paris (1257). The last step was to place the rose in the tier of lower windows, in which case it became the centre of a vast window composition, covering the whole end of the transepts, as in Rouen Cathedral.

In England the use of the rose window was usually confined to the transepts, although roses of great span were constructed in Byland Abbey and in the east front of Old St. Paul's, London. In Germany it was more frequently used as well in the Romanesque as in the Gothic period; a fine example is in the facade of the Cathedral of Strassburg. In Italy it was particularly used by the Lombard architects, as in San Zeno, Verona, and in the  Cathedral of Modena, and in the Tuscan Gothic churches like the Cathedrals of Siena and Orvieto. These rose were always filled with stained glasses of great beauty, adding not a little to the picturesque effect of the interior of the cathedral. (definition provided by the newadvent catholic encycolpedia)
Geometry

The basis of many churches is geometry and proportion. Numbers had a metaphysical significance, and were thought to have occult power. Every aspect of the medieval cathedral utilized that significace: the number of pillars in the choir, the ratio of the levels of in the triforium, etc. Rose windows are no exception to this rule.

                             1: the unity of all things, symbolized by a circle

                             2: duality and the paradox of opposites

                             3: the triangle, stability transcending duality

                             4: the square, matter, elements, winds, seasons, directions

                             5: the pentacle, man, ,magic, Christ's wounds

                              6: equiliubrium and balance of the soul, Solomon's Seal

                              7: the mystic number, the ages, planets, virtues, gifts of the Spirit

                              8: the octagon, baptism and rebirth

                              12: Perfection, universe, time, the apostles, the Zodiac, tribes
                                      of Israel, and the precious stones in the foundations of New Jerusalem
 

       The students of numerology assign the followin attributes to these numbers:
1 Creativity, independence, originality, ego, self
2 Empathy, cooperation, consideration, over-sensitivity, co-dependence 
3 Artistic expression, sociability, friendliness, superficiality, wastefulness
4 Practicality, application, loyalty, rigidity, repression
5 Freedom, adaptability, travel, inconsistency, abuse of senses 
 6 Love, responsibility, understanding, meddling, jealousy
7 Spirituality, mental analysis, wisdom, fault finding, suppression 
8 Executive ability, management, power, materiality, unscrupulousness
9 Artistic genius, humanitarianism, romance, emotionalism, dissipation 
11 Intuition, idealism, invention, insensitivity, fanaticism
22 Practical idealism, material mastery, get-rich-quick schemes, viciousness
 
 


Rose windows utilize geometry on three levels: physical, hidden, and symbolic.
The visual impact of the rose window is physical.
Every space is defined by another smaller geometric figure - a trefoil, a quatrefoil, rosette, or spherical triangle. Even the glasswork itself adds to this geometry. The hidden geometry defines the exact placement of every major feature of the rose window-relating to the radial elements, concentric divisions, and all to the center.
The symbolic geometry is found in the the numerical significance in the chart above. Circles, squares, triangles, stars, and, of course, the 12 major divisions typically found in rose windows all point to the finite and infinite, earth and heaven, or matter and spirit.

Of course, the geometric significance is rather an intellectual one and probably lost on most people other than in the pleasing proportions and the way the window draws the eye.