Sentence:  It took me from nine to ten days to grind and polish it ready for parabolising and silvering. I did this by hand labour with the aid of <WSD>emery</WSD>, but without a lathe. I finally used rouge instead of <WSD>emery</WSD> in grinding down the glass, until I could see my face in the mirror quite plain. 
Meaning of the word marked with <WSD> tags:  An impure type of corundum, often used for sanding or polishing.