2l8 PRINCIPLES OF RURAL ECONOMICS 



power to propel a boat eight miles in an hour as it does to propel 

 it four miles in the same time. The resistance of the water is 

 greater the greater the speed. Similarly with the plow ; to pull 

 it through the soil and turn the furrow at an increased rate of 

 speed requires more than a proportionally increased tension 

 on the clevis. Again, beyond a certain point increased exertion 

 produces more than proportionally increased fatigue. It is more 

 than twice as fatiguing to a team to double its rate of speed 

 beyond a good comfortable gait. 



While it is practically certain that three horses with a common 

 fourteen-inch plow could not plow three acres in a day as easily as 

 two could plow two acres, it is quite possible that if the size of the 

 plow were increased they could do it with the same ease. Here 

 again it is a question of finding the proper proportion among the 

 various parts of the combination. Theoretically the nature of this 

 proportion can be stated a little more exactly by means of the fol- 

 lowing illustration, though the practical application of the principle 

 always has to be worked out on the spot by experimentation. 



Let us assume that two horses, without overwork but working 

 up to their reasonable capacity, can plow two acres a day, whereas 

 three horses, with the same plow and the same fatigue to man 

 and beast, can plow not three acres but two and one half. One 

 half acre is then the result of adding a third horse to the team. 

 Does it pay ? Well, if the third horse would otherwise be stand- 

 ing idle, it doubtless would. But suppose it is a question of hiring 

 a third horse, or of keeping three horses on the farm instead of 

 two ; it would then be a question as to whether the value of the 

 one half acre of plowing was sufficient to pay the cost of his keep, 

 plus risk and deterioration, interest on his cost price, etc. If the 

 total cost of the horse is $i .50 a day, while plowing is worth only 

 $2.00 an acre, it is obviously a bad proportion, and two horses 

 are more profitable than three. But if his daily cost were any- 

 thing less than $i, then it would be a profitable combination. 



