238 On a Mode of erecting liyht Vaults 



In the* llth chapter, De 1'Orme speaks at length of domes 

 over quadrangular spaces as a new invention (invention fort 

 ingenieuse pour couper un globe quarrement), and boasts, 

 with justice, that it is cheaper, because it requires no ribs, and 

 is easier to execute because the section of the joints is simpler ; 

 and, finally, he describes several kinds of this vaulting, accord- 

 ing to the quadrilateral circle, triangle, and oblique line. 



Now, an invention which, in the time of Del'Orme, was still 

 called a la moderne, cannot easily be much older, and, com- 

 pared with the statement in BoissereVs great work on the 

 cathedral at Cologne, p. 16, according to which the north aisle 

 was vaulted after the year 1500, is, perhaps, to be placed only 

 in the beginning of the fourteenth century. 



According to De 1'Orme, Mathurin Fousse, Derand, and 

 De la Rue also wrote on vaults: M. de Lassaux is not ac- 

 quainted with their works ; but it would appear that they limit 

 themselves to stone-cutting, to which the French, as we know, 

 began at that time to attribute perhaps too great a weight. 

 Roland de Valois also, who certainly was acquainted with the 

 above work and used it, repeats, in his * Dictionnaire d' Archi- 

 tecture,' only the names of the separate ribs, without adding 

 anything with respect to the practical execution of the vaults 

 themselves. Rondalet, in his excellent Art de batir, limits 

 himself in the same manner to the rules for the section of the 

 joints of the ribs. 



The author has also endeavoured in vain to obtain oral infor- 

 mation. One mason, indeed, remembered to have heard from 

 his grandfather, that in keying these vaults it was very neces- 

 sary to avoid driving in the key-stone too hard, because if that 

 were done the sides would rise and belly. The last vault of 



straight lines, and the vertical or oblique lines only are curved. Every light ceiling 

 is composed of boarding on a frame, on which the former is nailed in a perpendi- 

 cular direction. Now, as in general a surface of boarding is not capable of being 

 bent into a sharp curvature, the boards must be fastened in a horizontal position 011 

 a frame or skeleton formed of curves. If, on the other hand, we would have 

 another flexible material for the covering of the frame, for instance hoops, which 

 are in all respects preferable, the frame may be of straight wood, and consequently 

 may be prepared at a much smaller expense ; and the curved surfaces may be, by 

 means of hoops nailed on perpendic\ilarly or obliquely, of such a kind as may 

 best be laid on, and ornamented, without further preparation, with hair mortar 

 (which ought to be mixed with hog's bristles), and consequently prove a consider- 

 able saving in the boarding and reeding. 



