OE SUBSOILING PLANT. 91 



Time required in Minutes : 



To turn 1 furrow ... 67 48 34 



Lost in various operations 

 (lifting plough at end of 

 furrow, 2 minutes ; return 

 8 minutes ; placing at start 

 of furrow 5 minutes), total 15 15 15 



Total required to open 1 fur- 

 row 219 yards in length 82 63 49 



Practical Work per hour: 



Length of furrow, in yards 158 207 262 



Area ploughed in square 

 yards, the width of the fur- 

 row being 25^ inches ... 112-8 149-4 187-2 



The practical results shown by this last line would be 

 modified if other lengths of furrows were considered, the 

 time spent in lifting the plough out of the furrow and placing 

 it in position at the starting point being independent of the 

 length of furrow considered. 



The depth of ploughing is generally fixed beforehand, and 

 the width follows The section of the sod and the resistance 

 of the soil per square inch give the mean hauling power 

 required on the cable, from this the number of horses required 

 to work the winding drum may be deduced, and from their 

 energy the speed of the plough.* 



We have already given several examples of the method 

 of calculating the different elements of work for winding 

 drums (traction of ploughs, power of teams, mechanical 

 yields) we must now give some practical indications resulting 



* If we designate by n the number of animals yoked to the drum ; t the 

 mean power (in kilogrammetres, 7 '233 foot-pounds, per second) which gach 

 horse may furnish (see page 65) ; m coefficient of reduction variable with 

 the number of animals in the team (see page 66) ; k the mechanical yield 

 of drum and cable varying between 0'8 and 0'9 ; p the depth of the furrow, 

 varying between 14 inches and 27 inches ; I the width of the furrow, equals 

 1'3 x p, varying between 15 inches and 35 inches; e the mean traction per 

 square inch of section of sod, varying between 330 Ibs. and 660 Ibs. ; v the 

 speed of the plough per second in decimal fractions of a yard. The equi- 

 librium of the system is given by the following formulae : 



ntmK=plev, 

 or by 



n t m K = 1 -3 p* e v. 



