(1696) In consequence of the sudden cooling thus caused , the rocks burst asunder and could be broken down further .If a fire is burned against an ore containing large amounts of pyrite or other sulphides , naturally considerable quantities of sulphureous fumes ( SO2 and H2S ) are formed , which not only have a bad smell , but are also far from healthy .The situation becomes even worse if the ventilation in the mine galleries is insufficient , for then , as a result of the continuous burning of a fire , at the same time a deficiency of oxygen arises .