A sketch underneath it shows a round pillar on which is indicated which part of its summit is to bear the weight:  “il pilastro sara charicho in . a . b.” (The column will bear the weight at a b.) Another note is above on the right side:_ Larcho regiera tanto sotto asse chome di sopra se (The arch supports as much below it [i. e. a hanging weight] as above it).

Pl.  C, No. 1 (C.  A. 303a).  Larger sketch of half section of the Dome, with a very complicated system of arches, and a double vault.  Each stone is shaped so as to be knit or dovetailed to its neighbours.  Thus the inside of the Dome cannot be seen from below.

MS. C. A. 303b.  A repetition of the preceding sketch with very slight modifications._]

[Figs. 1. and Fig. 2. two sketeches of the dome]

MS. Tr. 9 (see Fig. 1 and 2).  Section of the Dome with reverted buttresses between the windows, above which iron anchors or chains seem to be intended.  Below is the sketch of the outside._

PI.  XCIX, No. 3 (C.  A., 262a) four sketches of the exterior of the Dome.

C. A. 12.  Section, showing the points of rupture of a gothic vault, in evident connection with the sketches described above.

It deserves to be noticed how easily and apparently without effort, Leonardo manages to combine gothic details and structure with the more modern shape of the Dome.

The following notes are on the same leaf,_ oni cosa poderosa, and oni cosa poderosa desidera de(scendere); farther below, several multiplications most likely intended to calculate the weight of some parts of the Dome, thus 16 x 47 = 720; 720 x 800 = 176000, next to which is written: peso del pilastro di 9 teste (weight of the pillar 9 diameters high).

Below:_ 176000 x 8 = 1408000; and below:

Semjlio e se ce 80 (?) il peso del tiburio (six millions six hundred (?) 80 the weight of the Dome).

Bossi hazarded the theory that Leonardo might have been the architect who built the church of Sta.  Maria delle Grazie, but there is no evidence to support this, either in documents or in the materials supplied by Leonardos manuscripts and drawings.  The sketch given at the side shows the arrangement of the second and third socle on the apses of the choir of that church; and it is remarkable that those sketches, in MS. S. K. M. II2, 2a and Ib, occur with the passage given in Volume I as No. 665 and 666 referring to the composition of the Last Supper in the Refectory of that church._]

F.  The Project for lifting up the Battistero of Florence and setting it on a basement.

Among the very few details Vasari gives as to the architectural studies of Leonardo, we read:  “And among these models and designs there was one by way of which he showed several times to many ingenious citizens who then governed Florence, his readiness to lift up without ruining it, the church of San Giovanni in Florence (the Battistero, opposite the Duomo) in order to place under it the missing basement with steps; he supported his assertions with reasons so persuasive, that while he spoke the undertaking seemed feasable, although every one of his hearers, when he had departed, could see by himself the impossibility of so vast an undertaking."