1019.

In the Cathedral at the pulley of the nail of the cross.

Item.

To place the mass v r in the...

[Footnote:  On this passage AMORETTI remarks (Memorie Storiche chap.  IX):  Nell’anno stesso lo veggiamo formare un congegno di carucole e di corde, con cui trasportare in piu venerabile e piu sicuro luogo, cioe nell’ultima arcata della nave di mezzo della metropolitana, la sacra reliquia del Santo Chiodo, che ivi ancor si venera.  Al fol. 15 del codice segnato Q. R. in 16, egli ci ha lasciata di tal congegno una doppia figura, cioe una di quattro carucole, e una di tre colle rispettive corde, soggiugnandovi:  in Domo alla carucola del Chiodo della Croce.

AMORETTI’S views as to the mark on the MS, and the date when it was written are, it may be observed, wholly unfounded.  The MS. L, in which it occurs, is of the year 1502, and it is very unlikely that Leonardo was in Milan at that time; this however would not prevent the remark, which is somewhat obscure, from applying to the Cathedral at Milan.]

1020.

OF THE FORCE OF THE VACUUM FORMED IN A MOMENT.

I saw, at Milan, a thunderbolt fall on the tower della Credenza on its Northern side, and it descended with a slow motion down that side, and then at once parted from that tower and carried with it and tore away from that wall a space of 3 braccia wide and two deep; and this wall was 4 braccia thick and was built of thin and small old bricks; and this was dragged out by the vacuum which the flame of the thunderbolt had caused, &c.

[Footnote:  With reference to buildings at Milan see also Nos. 751 and 756, and Pl.  XCV, No. 2 (explained on p. 52), Pl.  C (explained on pages 60-62).  See also pages 25, 39 and 40.]

Remarks on natural phenomena in and near Milan (1021. 1022).

1021.

I have already been to see a great variety (of atmospheric effects).  And lately over Milan towards Lago Maggiore I saw a cloud in the form of an immense mountain full of rifts of glowing light, because the rays of the sun, which was already close to the horizon and red, tinged the cloud with its own hue.  And this cloud attracted to it all the little clouds that were near while the large one did not move from its place; thus it retained on its summit the reflection of the sunlight till an hour and a half after sunset, so immensely large was it; and about two hours after sunset such a violent wind arose, that it was really tremendous and unheard of.

[Footnote:  di arie is wanting in the original but may safely be inserted in the context, as the formation of clouds is under discussion before this text.]

1022.

On the 10th day of December at 9 o’clock a. m. fire was set to the place.

On the l8th day of December 1511 at 9 o’clock a. m. this second fire was kindled by the Swiss at Milan at the place called DCXC. [Footnote:  With these two texts, (l. 1—­2 and l. 3—­5 are in the original side by side) there are sketches of smoke wreaths in red chalk.]