ANCIENT EGYPTIAN LOCK. il7 



can be made from an examination of the lock alone? In 

 anfwer to this it may be noticed, that (ince all the pins in 

 the key muft be of equal height, the fecret will confift in their 

 relative diftances and pofitions on the face of the key ; and 

 that thefe diftances and pofitions can be eafily known by intro- 

 ducing a flick, or key without pins, into the hollow of the 

 bolt, and taking an impreflion (by means of a facing of foft 

 clay) of the holes intended to receive tlie pins. After this a but Its key may 



key may be made without difficulty : fo that we arrive at our ^^ "'''y ""^^^ 

 I / , , , ,• • • • r IT from the lock. 



conclunon, that though this ingenious pieCe ot mechanilm 



cannot be violated without its key, yet it is eafy to conflru<5l 



a key for that parpofe. 



We now come to the enquiry after that application of its Improvement by 



principles which may render it abfolutely fate. This is cer- y*^"^^;.' V '^*^""' 



., _,, , ., /-til i---n- dered fare, 



tamly poffible ; but not without conuderably diminilning its 



fimplicity. Befides feveral others, the following may be pro- 

 pofed : Let the dropping pin have an enlarged part, and a 

 tail of wire above and below. Let the lower tail fall into its 

 hole in the bolt, while the enlarged part falls into a focket 

 made for its reception. Under thefe circumflances the bolt 

 becomes faft : But when by raifing the pin the enlarged part 

 is clear of its focket, the bolt becomes free, and the lower 

 tail is prevented from flopping it by a groove left for its re- 

 ception. The bolt mull have a covering piece of board, 

 having a hole of the fize of the enlarged part of the pin, diredly 

 above the focket into which it falls, and a groove for its upper 

 tail ; the interval between the covering-piece and the bolt 

 itfelf being equal to the height of the enlarged part of Ihe pin. 

 By this means, when the pin is pulhed up, juft out of its 

 focket, the bolt will move freely ; but if it be puflied the leaft 

 quantity farther, the enlarged part will enter the hole in the 

 covering-board, and fet it faft, as if it were in the focket; fo 

 that a very precife diftance of elevation will be requifite, 

 Laftly, the lower pin may be (horter or longer at pleafure. 

 Now, if there be a number of thefe pins fo placed and ad- 

 jufted as to fall into their refpedive fockets at the pofition of 

 the bolt when fliut ; if their lower tails be of different lengths, 

 and a key be made to correfpond with them, and lift them all 

 to the proper height at once; the combination will be fuch as 

 cannot be made out by any impreflion or tentative procefs 

 upon the lock itfelf. For the evidence of a due length of any 

 4- one 



