Woodworking "Finishing" of Woodwork 27 



of bichromate of potash in water, applied with cheese cloth, each 

 part of the surface being treated once only. 



Walnut and mahogany may be treated as above, but after 

 staining and oiling should be French polished (see Section IV.) ; 

 and, indeed, oak is for many purposes improved by a thin layer of 

 French polish. French polish, or a fairly heavy wax polish, 

 preserves the wood from water, acids, and alkalies better than 

 any other preparation, and though it is a little more trouble, the 

 enhanced effect will adequately repay the extra labour expended 

 upon the work. 



NOTE. Wood screws, of iron or brass, are numbered according 

 to the following rule : 



No. 4 has a diameter of |", each succeeding number adding 

 aY' to the diameter of the screw. This applies to all lengths. 



The length of countersunk screws is measured " over all," that 

 of round-headed screws, from under the head. 



