©ESCRIPTION OF A SECRET LOCK. £>]() 



The face of the lock is fitted up, as we have obferved, with Coriftruftion f 

 five fcrew heads. The middle ftem, inftead of being provided a ^. cret lock a c- 

 with a wheel and ferril like the others, has a wheel of 45 in di- the proprietor, 

 ameter, 4 in thickncfs, and has 24 teeth of the depth of 3. 



Fig. I. PI. II. reprefents the face of the lock. A B is 230, 

 A A 67, and the five fcrew heads, R, are fpaced at equal 

 diftances. 



Fig. 2 reprefents the infide of the lock without its bolt. 

 The plan of the four ferrils with their fcrews, together with 

 the middle toothed wheel and the heads of the nuts, are vifible, 

 but the four flat wheels are concealed beneath the ferrils. 



The ferrils are inclofed in a rectangular box, 2 in thicknefs, 

 and about 28 in height at the longer fides. The fhorter are 34 

 jn height, and have an excavation or notch in them to the 

 depth of 8. The fides of this box are at the diftance of 6 from 

 the ferrils endwife, but only 2 as to the breadth. Tfre diftance 

 between the middle wheel and the nearefl ferrils is alfo 2, but 

 that between the contiguous ferrils is 5. 



In the four inner angles of the box are fixed four pillars, 

 P P P P, in thicknefs 6, in width 1 3, and about 35 above the 

 plate. Thefe pillars have at their extremities a rectangular 

 groove for the bolt to Aide in, and they are fixed by fcrews to 

 the long faces of the box, and by rivets to the end plates. The 

 fquare frame of the box is fattened to the face by two cocks 

 Z Z, which receive fcrews. 



The bolt is conftructed as follows : A thin bar of iron is 

 taken, of which the width C C, Fig. 3, is 67, and the length 

 C D, which is variable towards D, is 310 from F to C. It is 

 fitted with two edge bars C F, C F, of which the width is 5, 

 and another C C, only 4. At the end which is to form the 

 part of the bolt to (hoot out, a plate F F D D is fixed, of the 

 fame breadth as C C, but in length arbitrary. The depth of 

 the three edge bars is 6|, and cannot be feen in the figure. 

 That of the end plate depends on the ftrength intended to be 

 given. 



The two lateral edge bars C F have near their extremities a 

 projection x xf , x" x"', which exceed the edge bar by 3, and do 

 not come down to the face of the bolt by an interval of 3. In 

 thefe four fpaces the extremities of the pillar Aide, and they 

 ^hemfelves receive the projections x .r', x" x" J in their grooves. 

 3 The 



