THE ANIMAL AS A MOTOR. 



53 



Where the animal must develop maximum power 

 continuously at any considerable speed, the number 

 required for a specific work will always be greatly in- 

 creased. Thus, in coaching, the proprietors of mail- 

 coaches, even on the admirable highways of Great 

 Britain, maintain one horse per mile of route for each 

 coach and worked in fours, so that, going and return- 

 ing, each travels 8 miles per day, working only an hour 

 or less each day on the average. The coach weighs, 

 loaded, two tons, and its coefficient of friction on good 

 roads is about 0.035. Draught-horses at 2.5 miles an 

 hour are expected to do seven times the work of coach- 

 horses at 10 miles.* 



18. Tabulated Figures for the work of men and 

 animals follow, as given by Coulomb, Navier, Poncelet, 

 Rankine,f and others. Tables A, B, C, D, etc. 



According to Mr. Box, the work of men and animals 

 may be taken, in foot-pounds per minute, as : 



r— Hours per Day. > 





V 



4 



6 



8 



10 







3,730 



3,030 



2,640 



2,370 



" " " treadmill. . 



. . 130 



5,510 



4,490 



3,890 



3,460 





118 



4,420 



3,590 



3,100 



2,770 



Horse at a capstan. . 



.. 176 



24,780 



20,260 



17.520 



15,670 



Mule " .. 



. . 180 



16,530 



13,460 



11,680 



10,390 



Ox *' .. 



. . 120 



22,044 



17,980 



15,570 



13,920 



Ass " .. 



•• 157 



6,060 



5,610 



4,850 



4,320 



The average effort of a man at a winch should not 

 be assumed above 15 pounds for a day's work, although 

 more than double that figure may be easily attained 

 for a brief period. From 20 to 30 turns a minute is a 



* Barbour's Cyclopaedia of Manufactures, 

 f Steam Engine, Chaps. II., III. 



