60 



ANIMAL MECHANICS. 



servations made for more than a year, in all weathers, on the 

 daily labour of average workmen, gave the following results : — 



Work done, . . . 1046 ft. lbs. per minute. 

 Work, . . . 28O ft. tons per day (10 hours). 



The mean result of an ordinary day labourer, employed 

 with the box or swing-lift, is, therefore, 



" Box or swing-lift," .... 342 ft. tons. 



Example, No. 7. — A very accurate estimate may be formed 

 of the average day's labour, from observations formed on the 

 horizontal transport of weights, interpreted by the rules al- 

 ready laid down for the conversion of horizontal into vertical 

 transport. 



(a.) If a pedestrian be employed in walking only, without 

 load, it is found that 20 miles a day, with rest on Sundays, 

 give full employment to his strength, and that this amount 

 cannot be exceeded with prudence. From this assumption, 

 if we suppose the man's weight, including clothes, to be 

 160 lbs., we find — 



a. Horizontal transport of man ) 160 x 20 x 5280 

 walking without load, . ; 2240 

 = 7543 ft. tons. 



(b.) Coulomb observed the work done by porters employed 

 to carry goods 2000 metres, returning unloaded, and found 

 that each carried, in the course of the day, 348 kilos, in six 

 journeys, loaded with 58 kilos, at a time. If we suppose 

 each porter to weigh 70 kilos., we find the following result 

 for the horizontal transport : — 



Useful work, 2000 x 348 = 696000 kil. met. 



Fatigue work, 2000 x 2 x 70 x 6 = 1,680000 >, 



Total. 



2,376000 kil. met. 



