U. S. NATIONAL MUSEUM 



BULLETIN 173 PLATE 2 



MECHANICAL ELEMENTS. 



1. Roller, lever, and inclined plane (model; U.S.N.AI. no. 1812:>1). Sec p. 

 2. Chinese windlass (model; U.S.N.M. no. 307599). See p. 3. 

 3. Differential chain hoist (U.S.N.M. no. 309509). See p. 4. 



