42 SCIENCE OF THE MIDDLE AGES. PT. IL 



It seems almost certain that the Arabs knew a great deal 

 about gunpowder and some other mixtures which explode 

 when they are set on fire. Marcus Graecus, a man whose 

 origin is unknown, but who lived about the beginning of the 

 ninth century, says that if you mix together one pound of 

 sulphur, two of charcoal, and six of saltpetre, it will explode 

 when you light it and drive things into the air. This is 

 one of the ways in which gunpowder is still made. 



