53. Early in the year 1755, Etna began to show signs of disturbance; a great column of black smoke issued from the crater, from which forked lightning was frequently emitted. Loud detonations were heard, and two streams of lava issued from the crater. A new mouth opened near the Rocca di Musarra in the Val del Bove, four miles from the summit, and a quantity of lava was ejected from it. An extraordinary flood of water descended from the Val del Bove, carrying all before it, and strewing its path, with huge blocks. Recupero estimated the volume of water as 16,000,000 cubic feet, probably a greater amount than could be furnished by the melting of all the winter's snow on the mountain. It formed a channel two miles broad, and, in some places, thirty-four feet deep, and it flowed at the rate of a mile in a minute and a half during the first twelve miles of its course. Lyell considers the flood was probably produced by the melting, not only of the winter's snow, but also of older layers of ice, which were suddenly melted by the permeation of hot steam and lava, and which had been previously preserved from melting by a deposit of sand and ashes, as in the case of the ancient glacier found near the summit of the mountain in 1828. In November 1758, a smart shock of earthquake caused the cone of the great crater to fall in, but no eruption occurred at the time. 54. Great quantities of ashes, and some small streams of lava, were emitted from the crater in 1759, a little later the cone, which had been again raised by the eruption, gave way, and the greater part of it fell into the crater. Two parts of it however were left standing. 55. Severe shocks of earthquakes were felt on the east side of the mountain in 1763, and a new mouth opened in the Bosco di Bronte, ten miles from the town, between Monte Rosso and Monte Lepre. Four other mouths were afterwards opened in a line; they threw up quantities of scoriæ and ashes, and afterwards lava. In the middle of June several mouths opened on the south side of the mountain, and a fissure 2000 feet long opened downwards in a southerly direction. The lava divided into two branches, the larger of which was ten miles long and 250 feet wide, with a depth of 25 feet. 56. Several new mouths opened in the spring of 1766, and ejected large volumes of ashes, also streams of lava, which flowed in the direction of Nicolosi and Pedara. The Canon Recupero, one of the historians of Etna, witnessed this eruption, and narrowly escaped being destroyed. He had ascended a small hill 50 feet high, of ancient volcanic matter, in order to witness the approach of the lava stream which was slowly advancing with a front of two miles and a half. Suddenly two small streams detached themselves from the main stream, and ran rapidly towards the hill. Recupero and his guide at once hastened to descend, and had barely escaped when they saw the hill surrounded by lava, and in a few minutes it was melted down and sank into the molten mass.