Microscopical Essays. 125 



Y Is an appendage to the cutting engine, which is to be ufed 

 inftead of the micrometer fcrew, being preferred by fome prac- 

 titioners to it. It is placed over the triangular hole, and kept flat 

 down upon the furface of the brafs plate, while the piece of wood 

 is preffed againft a circular piece of brafs which is on the under 

 fide of it. * 



This circular piece of brafs is fixed to a fcrew, by which its 

 diftance from the flat plate on which the knife moves may be 

 regulated. 



Z, an ivory box, containing at one end fpare talc for the ivory 

 Ciders, and at the other fpare rings, for preffing the talcs together 

 and confining them to the Aider, 



C H A E 



