CATALOG OF THE MECHANICAL COLLECTIONS 5 



and had many simple machine combinations, these were all designed 

 to be operated by human muscular power, applied in most instances 

 with a reciprocating motion. Before it was possible to apply the 

 pulling effort of a beast to a machine it was necessary to develop 

 a continuous motion as an essential feature of the machine. Water- 

 raising wheels and rotary grain mills were the first devices to have 

 this essential feature, and a rotary mill turned by asses, mentioned 

 by Cato the Elder (232-149 B. C), is the earliest known application 

 of animal power to a machine. It was not until the abolishment of 

 slavery in the fourth century in Rome that cattle mills, which were 

 not unlike the slave mills, were generally used, and the use of the 

 geared animal mill, as it is known today, came after the development 

 of the geared water mills and windmills some time between the iso- 

 lated mention of one in 16 B. C. and their general use after 1200 A. D. 

 "Throughout medieval times a horse mill was practically identical 

 in construction Avith wind or water mills. The simple driving gear 

 placed in the lower story of the building comprised an upward shaft 

 revolved by the traction of one or more asses or horses harnessed 

 to shafts: attached to the shaft and near the ceiling, a large hori- 

 zontal toothed wheel actuated one or more spindle wheels connected 

 with the stones, which were placed above" (Bennett and Elton, 

 History of Coim Milling). 



A horse, walking around and turning a vertical shaft geared to a 

 chain drum, was used as late as 1928 to raise boats on a fairly large 

 marine railway at St. Michaels, Md., and the clay for the hand-made 

 brick used in the restoration of the Washington Birthplace at Wake- 

 field, Va., was tempered in a horse-powered pugmill erected there 

 for the purpose in 1931, 



Treadmills operated by the feet of men date back to water-raising 

 tread wheels of about the time of Christ, and they continue to be used 

 as penal devices today. No mention is found of the use of animals 

 on treadmills until a much later date. A donkey walking on the 

 inside of a large wooden wheel, first built in 1588, was used to raise 

 water from a well at Carlsbrooke Castle on the Isle of Wight as 

 late as 1919. Turnspit dogs running in wheels were early used to 

 revolve roasting spits, while dog-driven butter churns are still used 

 to some slight extent in this country. 



The unit of power that is most widely used to rate every source 

 of power (waterfalls, windmills, and all engines included) is based 

 on the effort of an animal. This unit, the horsepoioer, was de- 

 termined by James Watt to be the equivalent of 33,000 foot-pounds 

 of work performed per minute. One foot-pound is the work required 

 to raise a weight of 1 pound through a vertical distance of 1 foot, or 

 the work required to raise one-half pound 2 feet. Similarly 1 horse- 

 power is the equivalent of 33,000 pounds raised a foot every minute, 



