In 1904 Vesuvius had vented a lava flow which stopped in September, and its cone was sharp, with only a little crater and inner conelet on top. In 1905 lava had flowed from a northwest split. On April 4, 1906, a splendid black cauliflower cloud arose. The northwest flow stopped and a southern radial rift made lava mouths progress 500, 1,800, and 2,400 feet below the top, more than halfway down the mountain. From the lower mouth came glassy pahoehoe, or smooth destructive streams intensely incandescent and liquid, quickly cooling to aa, or sprouting rough fudge, black crusts, and clinker. The molten porridge flowed as a snaky avalanche into the masonry village of Boscotrecase. On April 7, at the crater, a column of boulder-laden steam shot up four miles, snapping with lightning. New lava mouths sent forking snakes crushing and swallowing parts of the village. A graveyard was neatly filled within its masonry wall, showing that internally the rocky torrent was a liquid. Meantime trajectories like those of a hose sent falls of gravel for miles, to Ottajano on the opposite side of the mountain. These also came from the central crater. On the west flank, at the observatory, the house was rocking, and heavy stones forced its occupants to retreat. Matteucci and his staff went halfway down the cone, to return next day. Explosions dwindled during the next fortnight, though one day an adverse wind from the crater carried carbon dioxide and hydrogen sulfide almost asphyxiating some persons. Thereafter cauliflower clouds of white steam arose and the noise of big avalanches was heard. The clinker field that invaded Boscatrecase was 16 feet thick, and houses were cut in two by a slaggy torrent. In Ottajano, on the opposite side of the mountain, flat tile roofs collapsed, buried under three feet of heavy gravel, some of it the size of an apple. Nearer the crater, boulders five feet in diameter were thrown a mile. The volcano was probably blocked inside by welling lava on the Boscotrecase side, which caused it to vomit steam and earthy avalanche material obliquely outward on the opposite, Ottajano, side.