[ ^^-' ] 



carefully learned, by marking how far it can be inferted into 

 the fliell without any ointment interpofed. The form of the 

 key and its lever is exhibited in fig. 6. in an horizontal fedlion 

 through the middle of them. 



Through the fliell of this cock are two round perforations 

 ■for two dudls through the cock, each, one inch diftant from 

 the other, and the fame from the end of the cock on either 

 fide : they are in a plane or fedlion paffing through the axis 

 of the key, and alfo through the axis of the barrel; and both 

 pafs through the ridge of metal T, at the back of the fliell. 

 The duft next the foialler end of the key (being a part of the 

 dud communicating with the receiver) is in diameter ^th and 

 the other dudl is only i^th of an inch : through the key alfo 

 are dudls anfwering to the perforations in the fliell ; but the 

 dudls in the key are not both in the fame fedion of it, but 

 one of them is at right angles to the other ; fo that when one 

 of the duds through the cock is open, the other will be always 

 fliut, and vice verfa. 



There is a continuation of each of thofe duds formed in 

 the piece of metal V, which is joined (by cement interpofed) 

 to the ridge of the fliell of the cock by four 'fcrews g, g, 

 £jr. I, by two openings (into the two duds in the piece of 

 metal) oppofite to thofe in the ridge ; and thefe duds in the 



piece 



i 



