INTRODUCTORY. 15 



Let us reckon a little. Suppose a man wishes to buy 

 a cow. Two are offered him, both four years old, and 

 which might probably be serviceable for ten years to 

 come. With the same food and attendance the first 

 will yield for ten months in the year, an average of 

 five quarts per daj', — and the other for the same term 

 will yield seven quarts and of equal quality. What 

 is the comparative value of each ? The difference in 

 yield is six hundred quarts per annum. For the pur- 

 pose of this calculation we will suppose it worth three 

 cents per quart — amounting to eighteen dollars. Is 

 not the second cow, while she holds out to give it, as 

 ffood as the first, and three hundred dollars at interest 

 besides ? If the first just pays for her food and attend- 

 ance, the second, yielding two-fifths more, pays forty 

 per cent, profit annually ; and yet how many farmers 

 having two such cows for sale would make more than 

 ten, or twenty, or at most, thirty dollars difference in 

 the price ? The profit from one is eighteen dollars a 

 year — in ten years one hundred and eighty dollars, 

 besides the annual accumulations of interest — the profit 

 of the other is — nothing. If the seller has need to keep 

 one, would he not be wiser to give away the first, than 

 to part with the second for a hundred dollars ? 



Suppose again, that an acre of grass or a ton of hay 

 costs five dollars, and that for its consumption by a 



