Each new trial was a lesson learned. It was only with time that they adjusted precisely the sufficient counterpoise to the thrust of the vaults; it was only by degrees that the pier's diameter was lessened, only with practice that was learned the placing of flying buttresses neither too high nor too low. At first many a flying buttress was made needlessly heavy. The solid wall in between the buttresses was not discarded all at once. In the first Gothic churches windows continued to be single lights, then two or three lancets were placed side by side, subsequently each light was subdivided by mullions, and gradually an elaborate fenestration developed. For a time, too, the round arch continued in use, and the earliest vault ribs were semicircular. With the fusion of the equilateral arch and the counterbutted intersecting ribs, the essence of Gothic architecture was achieved. Lesser consequences of the new form of vaulting followed in logical succession. Obeying the law that it is the thing borne which commands the form of the thing that bears, the ribs may be said to have drawn out of the sturdy pier of Romanesque art the clustered columns of Gothic gracefulness. Not a single beauty in a Gothic church but has a structural explanation. The soaring pinnacles that crown the buttresses are apparently mere ornaments, but in reality those gallant little bits of decoration are of sound engineering usefulness. By weighting the buttresses, they hasten to channel the transmitted lateral thrust of the vaulting into a vertical pressure, and they increase, too, the counterthrust of the flying buttress against the side walls. A clear comprehension of Gothic is impossible unless the fact be grasped that architecture is nothing if not structural, and that no decoration can veil a faulty skeleton. Ornamentation is the spontaneous blossoming of the structure, else it is meaningless--a principle many a modern architect might well digest. Too long has the most scientifically exact of architectures been judged by its embellishments, which often enough, in the hands of the copyist, do become a florid veneer without reason. The Gothic master-of-works was right when he said that nothing which was inherently needed could be ugly. No longer were flying buttresses hidden under the cover of wooden roofs. Proudly ranged about the church, those essential practical members became one of the distinctive beauties of the new science of building. Renan, with his treacherous half praise, has called the flying buttress a crutch needed by an architecture which, from its start, nourished the seeds of decay, since it was based on no sound constructive formula. Its success was a prestidigitator's trick, he said. Such criticism misunderstands the A B C of Gothic lore. Can a living limb be called a crutch? it has been aptly asked. The Gothic cathedral is not only the most complicated, but is also the most complete, organism ever conceived by man.