As for the analogy of the negation of the furnace, the impurity of iron, silver, and gold, which is what is attached to these bodies in metals from the origin of nature. They used fire to remove that, and they used fire by igniting the air, and they helped to move the air with the furnace. So the slag was negated except for two premises, which are fire and air. If these two forces did not exist, Scientific and practical, this malice has not been denied .