BOOK XXXIV. xxxiii. 128-XXXIV. 131 



the furnaces ot copper works. The difference 

 between them is that bubble is disengaged by wash- 

 ing but ash is not washed out. Some people have 

 given the name of ' bubble ' to the substance that 

 is white and very light in weight, and have said that 

 it is the ashes of copper and cadmea, but that ' ash ' 

 is darker and heavier. being scraped ofF the walls of 

 furnaces, mixed with sparks from the ore and some- 

 times also with charcoal. This material when 

 vinegar is applied to it gives ofF a smell of copper, 

 and if touched with the tongue has a horrible taste. 

 It is a suitable ingredient for eye medicines, 

 remedying all troubles whatever, and for all the 

 purposes for which ' ash ' is used ; its only difference 

 is that its action is less violent. It is also used as an 

 ingredient for plasters employed to produce a gentle 

 cooHng and drying effect. It is more efficacious for 

 all purposes when it is moistened with wlne. 



XXXIV. Cyprus ash is the best. It is produced 

 when cadmea and copper ore are melted. The ash 

 in question is the lightest part of the whole sub- 

 stance produced by blasting, and it flies out of the 

 furnaces and adheres to the roof, being distinguished 

 from soot by its white colour. Such part of it as is 

 less white is an indication of inadequate firing ; it is 

 this that some people call ' bubble.' But the redder 

 part selected from it has a keener force, and is so 

 corrosive that if while it is being washed it touches 

 the eves it causes blindness. There is also an ash 

 of the colour of honey, which is understood to indicate 

 that it contains a large amount of copper. But any 

 kind is made more serviceable by washing ; it is 

 first purified with a strainer of cloth and then given 

 a more substantial washing, and the rough portions 



223 



