414 NATURAL HISTORY. 



substances while they work ; which may make them 

 both to fume less, and to inflame less. 



Experiment solitary touching the materials of wildfire. 



783. It is conceived by some, not improbably, 

 that the reason why wild fires, whereof the principal 

 ingredient is bitumen, do not quench with water, is, 

 for that the first concretion of bitumen is a mixture 

 of a fiery and watery substance ; so is not sulphur, 

 This appeareth, for that in the place near Puteoli, 

 which they call the court of Vulcan, you shall hear 

 under the earth a horrible thundering of fire and 

 water conflicting together ; and there break forth also 

 spouts of boiling water. Now that place yieldeth 

 great quantities of bitumen ; whereas jJEtna and Ve 

 suvius, and the like, which consist upon sulphur, 

 shoot forth smoke, and ashes, and pumice, but no 

 water. It is reported also, that bitumen mingled 

 with lime, and put under water, will make as it were 

 an artificial rock ; the substance becometh so hard. 



Experiment solitary touching plaster growing as 

 hard as marble. 



784. There is a cement, compounded of flour, 

 whites of eggs, and stone powdered, that becometh 

 hard as marble : wherewith Piscina Mirabilis, near 

 Cuma, is said to have the walls plastered. And it is 

 certain and tried, that the powder of loadstone and 

 flint, by the addition of whites of eggs, and gum- 

 dragon, made into paste, will in a few days harden 

 to the hardness of a stone. 



