In 1810, when Rome was incorporated in the French Empire, the Governor, Baron Daru, placed the Colosseum under the direction of the Roman architect Valadier, to carry on regular excavations, which were continued for four years, from 1810 to 1814; of these works the Comte de Tournon[152], then prefect, has written an account. In 1812, under the French, the ruins of the walls and the surface of the vaults were weeded of the vegetation which threatened their ultimate destruction, and the uprooting of the shrubs had become necessary to save the walls. In sixty years they had again grown up so vigorously that another weeding was absolutely required, and in November, 1870, the whole of the ruins of the Colosseum were cleared of weeds and shrubs, under the direction of Signor Rosa, who was appointed by the Italian Government to superintend the works, and to carry on excavations on a large scale, from that building to the Forum Romanum. There is no doubt that it was quite time this clearing should take place, as the roots of the plants were in many parts displacing the stones, and would soon have done serious mischief. There was a great outcry against this necessary work by the botanists and the lovers of the picturesque, but archæologists must approve of it. Many things are now brought into view more clearly than they were before. A view of these excavations was taken and engraved in 1813. It represents clearly the passages round it, and two straight parallel channels down the middle of it for the naval fights, which were in reality not a representation of sea-fights but of river-fights. In 1814, and again in 1867, the subterranean passage leading from the Amphitheatre on the side next the Cœlian was excavated as a private speculation in search of treasure, which was not found; but the passage was left open as we now see it[153]. In 1864-5, considerable excavations were made between the Colosseum and the Cœlian, in search of treasure supposed to have been buried there, but only a subterranean passage was found. The work was interrupted by water gushing out in great abundance,—to such an extent that the area of the Colosseum was completely inundated, and the water was obliged to be drawn off by a steam engine[154]. The passage then discovered is still left open; the upper part of the vault only is removed, which formed the floor, or rather supported the floor, of another passage on the present level of the ground, leading from the _podium_, or lowest storey, towards the Cœlian. The point where the water gushed out and stopped the work was just outside of the site of the outer wall, long since destroyed on that part of the building. The great excavations of 1874 shewed that this passage turned to the left or south when it reached the outer wall, and followed the line of it until it joined the outer end of the long straight passage down the centre of the building.