THE SOIL AND SOIL FORMATION 59 



capital. As this excess is loaned and the interest earn- 

 ings minus the cost of running the bank is added, the 

 form of the capital becomes more complex. When some 

 of the loans result unfavorably, the books are com- 

 plicated by records of uncollected interest, mortgage 

 foreclosures, property rentals on real estate, charges to 

 the loss account, uncollected rental charges, etc. Rumors 

 of the insolvency of the leading owners of the bank, of 

 unreliability of the bank officers, and even defalcation, 

 may prejudice the minds of the public against the bank, 

 causing a falling off of the business, or even may result 

 in a run on the bank. The business thus becomes very 

 complex, and some very minor matter, as a true or 

 untrue rumor as to the solvency of the banks in the 

 town, or of the bank in question, may cause the bank 

 to decline. 



A soil is a far more complex store of wealth than a 

 bank. Its original capital is more indestructible, but 

 its ability to pay dividends rests on even more con- 

 tingencies than in the case of the ordinary bank. Even 

 where plants can draw upon the soil for all the mineral 

 matter they need without seriously reducing the amount 

 yearly made available, other conditions may determine 

 the yields of crops. Recent investigations indicate that 

 some soils are made infertile by very minute quantities 

 of substances poisonous to the plants. At first this 

 seems very strange, but a simple example from practices 

 in fish culture will illustrate how minute quantities of 

 poisons in solutions will act on living things. In a cer- 

 tain fish hatchery the water, as it runs from a spring 

 into the troughs where the little fish are kept, becomes 

 filled with a minute green plant called an alga. A 

 barrel of water containing sulphate of copper is placed 

 beside the spring, and from it a sufficient amount of this 

 copper solution is allowed to drip to give it a strength 

 of one part in 5,000,000, or one fifty-thousandth part of 



