4 BULLETIN 173, U. S. NATIONAL MUSEUM 



The diflferential hoist is a modern form of the old Chinese windlass 

 (see above). It was first suggested in this form by Thomas A. 

 Weston about 1858. It is the least efficient of the three hand hoists 

 exhibited, but with it one man pulling 77 pounds can lift 810 pounds 

 through 19 inches in one-half minute. 



With the screw-geared block, which has a mechanical efficiency of 

 about 40 percent, one man pulling 77 pounds lifts 1,600 pounds 12.8 

 inches in one-half minute. 



The ball-bearing spur-gear block is the most efficient of the three 

 (80-85 percent). With it one man pulling 77 pounds lifts 1 ton 26 

 inches in one-half minute. 



ADDITIONAL MODELS IN THE COLLECTION, NOT DESCRIBED 



Apparatus for raising aud lowering weights (chain hoist), Patent Office model, 

 Patent no. 99?31, January 25, 1870, issued to J. Piclvering. U.S.N.M. no. 308807. 



Apparatus for raising and lowering weights (chain hoist). Patent Office model, 

 Patent no. 119527, October 3, 1871, issued to Thomas Moore. U.S.N.M. no. 308801. 



Chain hoist. Patent Office model, not identified. U.S.N.M. no. 308800. 



Speed governor and friction brake (chain windlass), Patent Office model, 

 Patent no. 212339, February 18, 1879, issued to T. A. Weston. U.S.N.M. no. 

 308830. 



Friction bralce and clutch for hoisting drum, Patent Office model, Patent no. 

 212338, February 18, 1879, T. A. Weston. U.S.N.M. no. 308829. 



Chain hoist, Patent Office model, not identified. U.S.N.M. no. 308851. 



Ship steam windlass, models presented by the American Ship Windlass Co. 

 U.S.N.M. no. 160186. 



Hand windlass, 1876, invented and presented by T. S. Allen. U.S.N.M. no. 

 160185. 



Hand windlass, 1880, invented and presented by T. S. Allen. U.S.N.M. no. 

 160324. 



Capstan, Patent Office model, not identified, U.S.N.M. no. 308539. 



"Providence" steam windlass and capstan, 1886, gift of American Ship Wind- 

 lass Co. U.S.N.M. no. 57053. 



Hoisting pulley and worm gear apparatus (chain hoist), Patent Office model, 

 Patent no. 218223, issued to A. Box, August 5, 1879. Transfer from the United 

 States Patent Office. U.S.N.M. no. 311179. 



Converting reciprocating motion to rotary motion, Patent Office model, not 

 identified. Transfer from the United States Patent Office. U.S.N.M. no. 311180. 



Pawl and ratchet, Patent Office model. Patent no. 464838, issued to Thomas 

 Johnson, December 8, 1891. Transfer from the United States Patent Office. 

 U.S.N.M. no. 308844. 



ANIMAL POWER 



Dogs and horses were domesticated and used for transport and 

 burden as long ago as the New Stone Age, 12,500 to 6,000 years before 

 Christ, and other animals as they came under man's dominion were 

 trained to pull and carry. It is not until about 200 B. C, however, 

 that any mention is made of animals used for power jourposes. 

 Though the ancients knew all the elements of later-day machines 



