He went so far as to say that one of these spirits in the Saxon mine of Annaberg destroyed twelve workmen at once by the power of his breath.
At the end of the sixteenth century we find a writer on mineralogy complaining that the mines in France and Germany had been in large part abandoned on account of the "evil spirits of metals which had taken possession of them." Even as late as the seventeenth century, Van Helmont, after he had broken away from alchemy and opened one of the great paths to chemistry--even after he had announced to the world the existence of various gases and the mode of their generation--was not strong enough to free himself from theologic bias; he still inclined to believe that the gases he had discovered, were in some sense living spirits, beneficent or diabolical.
But at various.

periods glimpses of the truth had been gained.

The ancient view had not been entirely forgotten; and as far back as the first part of the thirteenth century Albert the Great suggested a natural cause in the possibility of exhalations from minerals causing a "corruption of the air"; but he, as we have seen, was driven or dragged off into, theological studies, and the world relapsed into the theological view.
Toward the end of the fifteenth century there had come a great genius laden with important truths in chemistry, but for whom the world was not ready--Basil Valentine.

His discoveries anticipated much that has brought fame and fortune to chemists since, yet so fearful of danger was he that his work was carefully concealed.

Not until after his death was his treatise on alchemy found, and even then it was for a long time not known where and when he lived.