The thing is accomplished without trouble， without effort， without reaction，--following a natural and tranquil law. It is a graft which shoots up， a sap which circulates， a vegetation which starts forth anew. Certainly there is matter here for many large volumes， and often the universal history of humanity in the successive engrafting of many arts at many levels， upon the same monument. The man， the artist， the individual， is effaced in these great masses， which lack the name of their author； human intelligence is there summed up and totalized. Time is the architect， the nation is the builder.
Not to consider here anything except the Christian architecture of Europe， that younger sister of the great masonries of the Orient， it appears to the eyes as an immense formation divided into three well-defined zones， which are superposed， the one upon the other： the Romanesque zone*， the Gothic zone， the zone of the Renaissance， which we would gladly call the Greco-Roman zone. The Roman layer， which is the most ancient and deepest， is occupied by the round arch， which reappears， supported by the Greek column， in the modern and upper layer of the Renaissance. The pointed arch is found between the two. The edifices which belong exclusively to any one of these three layers are perfectly distinct， uniform， and complete. There is the Abbey of Jumiéges， there is the Cathedral of Reims， there is the Sainte-Croix of Orleans. But the three zones mingle and amalgamate along the edges， like the colors in the solar spectrum. Hence， complex monuments， edifices of gradation and transition. One is Roman at the base， Gothic in the middle， Greco-Roman at the top. It is because it was six hundred years in building. This variety is rare. The donjon keep of d'Etampes is a specimen of it. But monuments of two formations are more frequent. There is Notre-Dame de Paris， a pointed-arch edifice， which is imbedded by its pillars in that Roman zone， in which are plunged the portal of Saint-Denis， and the nave of Saint-Germain des Prés. There is the charming， half-Gothic chapter-house of Bocherville， where the Roman layer extends half way up. There is the cathedral of Rouen， which would be entirely Gothic if it did not bathe the tip of its central spire in the zone of the Renaissance.*** This is the same which is called， according to locality， climate， and races， Lombard， Saxon， or Byzantine. There are four sister and parallel architectures， each having its special character， but derived from the same origin， the round arch.
~Facies non omnibus una， No diversa tamen， qualem~， etc.
Their faces not all alike， nor yet different， but such as the faces of sisters ought to be.
** This portion of the spire， which was of woodwork， is precisely that which was consumed by lightning， in 1823.
However， all these shades， all these differences， do not affect the surfaces of edifices only. It is art which has changed its skin. The very constitution of the Christian church is not attacked by it. There is always the same internal woodwork， the same logical arrangement of parts.
Whatever may be the carved and embroidered envelope of a cathedral， one always finds beneath it--in the state of a germ， and of a rudiment at the least--the Roman basilica.
It is eternally developed upon the soil according to the same law. There are， invariably， two naves， which intersect in a cross， and whose upper portion， rounded into an apse， forms the choir； there are always the side aisles， for interior processions， for chapels，--a sort of lateral walks or promenades where the principal nave discharges itself through the spaces between the pillars. That settled， the number of chapels， doors， bell towers， and pinnacles are modified to infinity， according to the fancy of the century， the people， and art.
The service of religion once assured and provided for， architecture does what she pleases. Statues， stained glass， rose windows， arabesques， denticulations， capitals， bas-reliefs，--she combines all these imaginings according to the arrangement which best suits her. Hence， the prodigious exterior variety of these edifices， at whose foundation dwells so much order and unity. The trunk of a tree is immovable； the foliage is capricious.