"On the Illinois fields advantage is taken of these relations in the developing of systems of permanent agriculture. You see, if the phosphate produces more clover, then more clover can be plowed under on that land; or, if the crops are fed, then more manure can be returned to the phosphated land than to the land not treated with phosphate and not producing so large crops. Really the phosphate is not given full credit for what it has accomplished in the Ohio experiments; because, while the land receiving phosphated manure has produced about one-fourth larger crops than the land receiving the untreated manure, the actual amounts of manure applied have been the same, whereas one-fourth more manure can be produced from the phosphated land and if this increased supply of manure were returned to the land it would increase the supply of nitrogen and thus make still larger crop yields possible."
"That is surely the way it would work out in practical farming," said Mr. West. "I think I did not tell that $4.80 a ton is the lowest quotation I have been able to get as yet for ground limestone delivered at Blue Mound Station."
"That would make its use prohibitive," said Percy. "You ought to get it for just one-fourth of that, or for $1.20 a ton. In Illinois we can get it delivered a hundred miles from the quarry for $1.20 a ton. It costs no more for a thirty-ton car of ground limestone than the farmer receives for a cow; and the cost of a car of fine-ground natural phosphate is about equal to the price of one horse."
"Of course, our limestone supplies are essentially inexhaustible," said Mr. West, "but is that also true of our natural phosphate deposits?"
"It is not true of the high-grade phosphate," replied Percy; "for, according to the information furnished by the United States Geological Survey, it is evident that the known supplies of our high-grade phosphate will be practically exhausted in fifty years if our exportation continues to increase at the prevailing rate. After that is gone we may then draw upon our low-grade phosphate deposits, which though probably not inexhaustible are known to be exceedingly extensive."
CHAPTER XXXI
THEORIES VERSUS FACTS
PERCY planned to walk to Blue Mound to take the three-thirty train that Saturday afternoon; but Adelaide's parents both insisted that she would willingly drive to the station, and the grandmother discovered that she needed a certain kind of thread which Adelaide could then also get at the store.
"Certainly," said Adelaide, with some merriment, "I always enjoy our departing guests to the train."
"Very well," replied Percy. "If you must go to get the thread and will permit me to be the coachman, I shall be satisfied, for you will be home early."