7:50 a.m.
This immense rising of thirty streams at once , without one drop of water having fallen on the sea-coast , gives some idea of the cataracts which must pour down upon the summit from the storm-clouds gathered around the crater . '' `` Hundreds of agonized people , '' writes Heilprin , in his great scientific work on the catastrophe , `` had gathered to their devotions in the Cathedral and the Cathedral Square , this being Ascension Day , but probably there were not many among them who did not feel that the tide of the world had turned , for even through the atmosphere of the sainted bells , the fiery missiles were being hurled to warn of destruction . The fate of the city and of its inhabitants had already been sealed . `` The big hand of the clock of the Military Hospital had just reached the minute mark of 7:50 a.m. when a great brown cloud was seen to issue from the side of the volcano , followed almost immediately by a cloud of vapory blackness , which separated from it and took a course downward to the sea . Deafening detonations from the interior preceded this appearance , and a lofty white pennant was seen to rise from the summit of the volcano . `` With wild fury the black cloud rolled down the mountain slope , pressing closely the contours of the valley along which had previously swept the mud-flow that overwhelmed the factory three days before , and spreading fan-like to the sea . `` In two minutes , or less , it had reached the doomed city , a flash of blinding intensity parted its coils , and St. Pierre was ablaze .