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ADDENDA. 



probably throw some light on what the Marquis may have 

 actually intended. Being desirous to construct a model 

 screw, some years ago, the author designed the following 



OO 



method of making one of tin or zinc, which may be 

 easily shown by cutting out the same in thin paste 

 board. Form a number of discs of thin metal like 

 No. 1, say three inches diameter, with a hole in the 

 centre one inch diameter, and the metalcut through at 

 A. Eivet, solder, or otherwise fasten them together, 

 commencing by placing No. 2 on No. 1 ; now secure the 

 cut edge of A, to the similar edge of 6, and so on in 

 succession, until a sufficient pile is obtained. They may 

 now be extended to form a screw, as in No. 3, of any 

 desired pitch. The minuter details of construction will 

 be obvious to any clever artizan. 



