Towards the end of January a crowd wrecked the offices of the tax-collector beside the Porta Ticinese; next day there was rioting near Pavia. The cause of the latter disturbance was an attempt made by a French soldier on the chastity of a peasant girl, who struck her assailant with a broom handle and was then threatened by him with an axe. She screamed; her father ran up with a cudgel and was killed by the soldier. Then the crowd fell upon the soldier and he was killed; after which the French drew on the populace and sacked the village.
When the news of this outrage reached Milan it acted like a spark upon gunpowder. The people poured into the squares, the streets, the market-places, shouting 'Down with the king! Down with Trivulzio! Death to the foreigners! Viva Il Moro!'
The French troops were too few to withstand attack from the three hundred thousand inhabitants of Milan. Trivulzio placed guns upon the tower which for the present was in use as the cathedral belfry, but before giving the order to fire on the crowd he tried one more effort at pacification. He was hustled, hunted into the Palazzo del Comune, and would have perished there but for the timely intervention of the Swiss mercenaries. Then ensued burning and pillaging; torture and murder of all foreigners and their sympathisers who fell into the hands of the citizens. On the 1st of February Trivulzio fled, leaving the fortress in charge of the Captains d'Espe and Codecara. That very night Il Moro returned from Germany, and was received with great joy by the town of Como; all Milan anxiously awaited him as its saviour.
In these last days of the revolt, when the streets were being wrecked on all sides by the cannonade, Leonardo transferred his household to the ample cellars of his house, contriving living-rooms of tolerable comfort, and storing everything of value: pictures, drawings, manuscripts, scientific instruments.
He had definitely resolved to enter Cæsar Borgia's service, and was to present himself in Romagna not later than the summer of 1500; meanwhile he proposed to visit his friend, Girolamo Melzi, at his villa of Vaprio in the vicinity of Milan, living there in retirement till the disturbances were at an end. On the morning of February the 2nd, the Feast of the Purification, Fra Luca brought him the tidings that the castle had been flooded. A Milanese, Luigi da Porto, who had been in Trivulzio's service, had deserted to the rebels, first opening all the sluices which fed the moats of the fortress. The water spread over the circumjacent lands, reaching to the walls of the Rocchetta; and, making its way into the magazine and provision stores, almost forced the French to surrender, which was precisely what Messer Luigi had hoped. The flood had also overflowed the canal, had inundated the low lying suburb of Porta Vercellina, where was situated the Monastery delle Grazie. Fra Luca expressed grave fears for Leonardo's Cenacolo and offered to go with him and see how it fared.
The painter, feigning indifference, replied that he was too busy, and that he believed the height of the fresco would preserve it from injury. No sooner, however, was he rid of Pacioli than he hastened to the convent refectory, on the brick floor of which pools were still left, and where there was a pervading odour of miasma and stagnant water. A monk told him that the flood had risen to the fourth of a cubit.
The Cenacolo had not been painted in water-colours, according to the usage for fresco; such process requiring a rapidity of execution alien to Leonardo's genius.
'A painter who has no doubts will have small success,' he used to say; and for his doubts, his vacillations, his experiments, corrections, and extreme slowness, only the medium of oil was suitable. It was in vain that experienced masters told him that oil paints were impossible for a damp wall standing on the verge of a marsh. His love of experiment, and of new paths and devices induced him to disregard all warnings; he mixed his paints in a special way, and prepared the wall by coating it first with clay, varnished and oiled, then with a mixture of mastic, pitch and plaster.
Having dismissed the monk, Leonardo crossed the still soaking refectory floor, and stepped close to examine his picture. The transparent and delicate colours seemed uninjured, and not even blurred; however he took a magnifying-glass and explored the surface in every part. To his dismay, there in the left-hand corner, just where the tablecloth was represented hanging in ample folds by the feet of St Bartholomew, he discovered a small crack; beside it the colours were already fading, and on the surface was a white velvety patch, scarce observable, but the beginning of mould. Sudden paleness overspread Leonardo's features; he composed himself, however, and continued his examination with minuter care. Very soon he realised what had happened. The first coating of varnished clay had bulged in consequence of the damp and had come away from the wall, raising the upper coating of plaster which carried the paint; and in the plaster tiny almost invisible cracks had formed, through which a salt sweat exuded from the porous brickwork. The Cenacolo was doomed. The colours might last forty or fifty years and Leonardo himself never see their decay, but it was impossible to doubt that this his greatest work must irretrievably perish. He stood looking at the face of his Christ; realising for the first time how dear to him was this, his supreme creation.
The ruin of the Cenacolo, the destruction of the Cavallo, snapped the last threads which bound him to men, which united him to friends perhaps still unborn. His soul had long been solitary; now his solitude was deeper than before. The clay of the Colossus, resolved into dust, was the sport of the winds of heaven; mould was gathering on the very countenance of the Lord, dimming its outline, blurring and fading its colours. All that had been his very life was vanishing as a shadow.