FACTORS OF AGRICULTURAL PRODUCTION 219 



]n general we may state the law thus : If you take one part 

 of i;he combination the plow in the foregoing illustration 

 as the basis, or the fixed unit, and vary the other factors, the 

 horses, for example, the law of proportion requires that the 

 last unit added to the variable factor, the third horse in the fore- 

 going illustration, must add to the product as much as it adds 

 to the cost; and, moreover, that it will pay to add to that 

 factor so long as the last unit added will add to the product 

 anything above what it adds to the cost. This statement of the 

 law sounds formidable, no doubt, but it is a law which must be 

 followed if the largest success is to be attained. However, most 

 successful farmers approximate pretty closely to the law, fre- 

 quently without knowing that it is a law. 



The advantage of knowing that it is a law is that it enables 

 a farm manager, if he cares to do so, to substitute methods 

 of exact experimentation for general good judgment in deter- 

 mining such questions as how many horses to use to each plow, 

 what size of plow to use with each team, how large a team and 

 plow to put in charge of each man, etc. The same law is involved 

 in the question of how many acres to cultivate with each man and 

 team, how large a ration and in what combination to feed to his 

 animals, and a multitude of others which the farm manager must 

 decide rightly or wrongly, offhand or by the methods of exact 

 experimentation. This law, it may be remarked, is merely a 

 more general statement of the law of diminishing returns from 

 land, as explained in preceding pages. It may be further eluci- 

 dated by means of the figures on the following page, which are 

 assumed arbitrarily for purposes of illustration. 



I ,et us assume that the basis, or the fixed unit, in the plowing 

 combination is one man. He may plow with one, two, three, 

 four, or as many as eight horses, using different plows suited to 

 the number of horses in the team. Let us assume further that 

 with one horse he can plow one acre. If that be true, it is 



