242 On Polishing Metals. 



wood, properly shaped, so as to penetrate into the hollows, and 

 act upon the raised parts. When the first coarse marks are 

 thus removed, they then proceed to remove those left by the 

 pumice-stone. In order to this, they employ finely powdered 

 pumice-stone, which they grind up with olive-oil, and employ 

 it upon felt, or upon small pieces of soft wood, such as that of 

 the willow or sallow. It is important, in these manipulations, 

 to observe an important rule, which is never to proceed from 

 one operation to another, before previously washing the pieces 

 of work well with soap and water, by means of a brush, in or- 

 der entirely to remove the pumice-stone, used with water, before 

 employing it with oil, and likewise never to use those tools for 

 succeeding operations, which had been used in preceding ones ; 

 each stage of the operation requiring particular tools, and which 

 should be kept in closed boxes, in order to prevent the powders 

 from being diffused or scattered about when not in use. With- 

 out taking these precautions, which must be particularly and 

 minutely attended to, we should be liable to make fresh scratches 

 instead of removing them. 



After removing the marks left by the coarse pumice-stone 

 and water, by means of finely grounded pumice-stone and oil ; 

 to know which, we should wash it with soap and water, and 

 dry it well with a linen cloth ; we must then examine it 

 with a lens or magnifying-glass, to see whether any scratches 

 yet remain ; if not, we may proceed to the polishing. The 

 softer metals are polished in different manners, according to 

 their size and uses ; the larger gold works arc, however, gene- 

 rally burnished, but the smaller gold works in jewellery, &c. 

 and those in brass for watch-work, are not burnished, but po- 

 lished. The following are the manipulations: — After having 

 removed with oil-stone powder the marks of the file, &c. they 

 smoothen them with blue and grey stones, and plenty of water : 

 there are two kinds of these stones, the one soft and the other 

 hard ; the first is designated by Brongniart, under the name of 

 Argillaceous Schistus, and is the kind in question ; the second 

 kind is named by the above mineralogist Schiste Coticule : this 

 serves to sharpen tools upon. The pieces of watch-work are al- 

 ways smoothened in this manner, until all the marks disappear, 

 and which is known by washing them in the manner above 

 mentioned with soap and water. 



