44 TRENCHING AND STJBSOILING 



negligible ; in any case, they are much less than those- 

 resulting from the union of the animals in a single team 

 executing the same work by direct traction on the plough. 



AREA PLOUGHED. 



The surface ploughed per day with a horse-gin depends 

 greatly on the length of the furrows and the size of 

 the plot. It depends also on the experience of the 

 workmen, and the skill with which they execute the 

 different works. It may be approximately calculated as 

 follows : The horse at the pole travels at an average 

 speed of 35^ inches per second, that is to say, 177 feet per 

 minute. The length of the pole is generally to the 

 diameter of the drum as 10 is to 1 ; the plough travels with 

 a speed ten times less, that is to say, 17*7 feet per minute. 

 If the width of the sod is 19 J inches, the surface ploughed 

 will be 28*5 square feet per minute ; and for ploughing 4 

 poles it would require 37 minutes, without stoppage, inter- 

 ruption, or breakage. But, taking the plough back to the 

 starting point, accidental stoppages, and unforeseen accidents., 

 absorb a time equal to that usefully used for plough- 

 ing, so that one hour and fifteen minutes are usually 

 required to plough 4 poles. In one day's work of ten 

 hours an area of 32 poles can, therefore, be ploughed. With 

 the movable gins, the conditions are more favorable, 

 4 poles per hour can be ploughed, that is to say, 40 poles 

 per day. One cannot depend on more rapid work. 



In shows and in public trials greater speeds have been 

 attained ; but the work required from the men and animals 

 was excessive, and could not be performed continuously. 



COST OF TRENCHING OR SUBSOILING WITH HORSE-GINS. 

 The estimation of the cost comprises 1st, the interest on 

 the outlay for plant ; 2nd, the expense for wear and tear ; 

 3rd, the daily expense of the work. 



A trenching plant, gin, plough, and accessories, cost on 

 the average, 80. This sum must be written off in ten 

 years. Taking the interest on the capital at 5 per cent., 

 the amount to be written off per annum is 10 10s. If we 

 assume that we plough 12^ acres every year, and that we 

 plough 40 poles every day, the machine will work 50 days 

 in the year. The daily expense to be written off is ^^* 

 = 4s. 2d. 



