ANIMAL MECHANICS. 



59 



Example, No. 5. — The paviours of Dublin make 78 blows of 

 the rammer in 2 m ' 45 s ', and then rest for 3 m - 30 s - ; their ram- 

 mer weighs 5 st. 9 lbs., and is lifted through 16 inches each 

 stroke; and their labour is continued each day for 10 hours. 

 Let us calculate from these data the work done per day. 



The time of labour is to the time of rest as 165 to 210; 

 hence, the time of labour is to the whole time as 165 to 375 ; 

 therefore, in the day of 10 hours the number of minutes of 

 labour is 



10 x 60 x 16c 



= 204 minutes ; 



375 



but in 2| minutes 79 lbs. are lifted 78 times through 16 inches. 

 Hence the work done in 2| minutes is 



79 x 78 x = 82i6lbs. ; 



and the work done in a whole day of 10 hours, is 



8216 x -^i= 788736ft. lbs.; 



which, divided by 2240, gives us 



Daily work of paviour, . . . 352 ft. tons. 



Example, No. 6. — In the construction of the Oxford and 

 Birmingham railway, a " box-lift" was employed in the cut- 

 tings, identical in principle with that used by Captain Coignet 

 (Example, No. 2), and the average result of more than a year's 

 observation on average workmen, in all weathers, was taken, 

 with the following results : — 



Work done, 15 10 ft. lbs. per minute. 



Daily work (10 hours), . 404 ft. tons. 



On the same railway a " swing-lift" was used, in which 

 part of the work of the labourers was employed, not in rais- 

 ing materials, but in shifting the position of the "lift." Ob- 



