64 The Bulletin. 



PHOSPHATE ROCK AS A SOURCE OF PHOSPHORIC ACID. 



Cyril G. Hopkins, Illinois Experiment Station, Urbana, 111. 



I very greatly appreciate the honor of being invited to come to North Caro- 

 lina to meet the North Carolina farmers and landowners. I feel that you 

 have put upon me a pretty difficult subject to talk about, but fortunately 

 I do not know much about it, and all that I need to do is to give you the 

 information that exists. 



I feel that I may call your attention to the fact that, as a general rule, 

 farmers are theoretical, while scientific men are practical. You know we are 

 wont to say that in another way. Farmers ordinarily consider themselves as 

 being practical, and you hear a great deal about the scientist being called a 

 theorist ; but the facts are that the terms should be changed around. Prob- 

 ably the most thorough theorist we have is the farmer, and the scientific man 

 is practical so far as his science goes. 



I should like to call your attention, too, to the fact that principles are dis- 

 covered by investigation and not by practice. Principles are established by 

 experiments and not by experience. We are too much inclined to think that 

 the thing we have been doing all our lives is the right thing to do; that we 

 have had practice in it, that wo have had experience in it, and therefore it is 

 established. Sometimes this is the truth, sometimes it is error, for, as I 

 said, principles are established by investigation and experiment, not by practice 

 and experience. I have not much doubt but there are people in the' audience 

 who. if they wanted to dig a well somewhere and get good water, would get a 

 water-witch to go and witch for them. There are some of these people in 

 Illinois. There is absolutely no basis for It but experience, yet some men will 

 say, "I know that is the right way to get water, because I know where it has 

 been found twice that way." I would suggest that next time you find a water- 

 witch who is dead sure about it. you tie a handkerchief around his eyes and 

 see if he finds the water twice in the same place. The one I trie<l could not 

 find it twice in the same place, with his eyes shut. lie had to see with his 

 eyes to find the water twice in the same place. 



Then, again, there are people, a good many, who do a good deal of their 

 farm work with the signs of the moon as their guiding agency. They plant 

 potatoes in the dark of the moon in order that the crop will grow underground 

 instead of growing above gi'ound. But experiment does not bear this out at all. 

 I mention these facts to call your attention to the common beliefs among us 

 that have no basis in fact. 



One of the best potato growers, if not the best in the United States, is 

 T. B. Terry, of Ohio. Some one once asked him if he believed in planting 

 potatoes in accordance with the moon theory. "Certainly," he said, "I believe 

 in planting according to the moon ; but the idea that you should plant in the 

 dark of the moon is wrong ; you should plant in the light of the moon, so that 

 you can see to work later at night." 



Let me give you another illustration that will help you to understand why 

 experience does not establish principles. You have found, every one of you, 

 that if you lived past the Fourth of July, then you have lived another year 

 after that. Now, you are trying it this year again, and you have tried that, 

 some twenty times, some fifty times, some seventy times. Always you have 

 found that if you lived past the Fourth of July you have lived another year. 

 It has never failed. That has been your experience, has it not? But does it 

 establish a principle? Not at all. Experience does not establish principles. It 

 must be done by experiment where the factors are under control and you can 

 eliminate all the factors except the one you are working out. 



Professor Williams told me this morning that in North Carolina it was a 

 rather common practice for farmers to pull ofC the suckers from the corn in 

 ordinary seasons. Why do they do it? Do you know? Because their fathers 

 before them did it. There has been a lot of investigation conducted along that 

 line, including some at Raleigh, and the regular result is that it decreases the 

 yield when it is actually tried. They get a larger yield where they do not 

 pull off the suckers. The corn plant knows what it is about when it puts out 

 suckers, either in making a bigger ear on the cornstalk or in making an ear on 



