5o6 ELEMENTARY BIOLOGY 



along in doubt and dread until the crop is ripe. And when the 

 crop is in, they rejoice as those coming to the end of a danger- 

 ous journey, and again they have their ceremonials and magic. 



We may observe similar attitudes toward problems of health. 

 Before people knotv what causes plague or malaria or tuberculosis, 

 before they know what kills their sheep and their potatoes, they are 

 just as fearful, just as superstitious, as they were during the Dark 

 Ages. In those times when witches were burned for bringing on 

 plague by uttering wicked words, or when foreigners were tortured 

 for poisoning wells by making wicked signs, no one knetv and 

 everyone feared and suspected. 



524. The measure of control. We have seen that the use 

 of tested knowledge to solve human problems may bring about 

 measurable results ; that is, we can measure what difference it 

 makes whether we use the scientific method or some other 

 method. Thus, we can measure how much work it takes to pro- 

 duce a given quantity of potatoes with the use of suitable fertilizer 

 and how much it takes to produce the same without fertilizer, 

 and so find the advantage of one method over the other. 



The following table shows the number of hours of human labor 

 required to produce by machinery, under conditions that prevailed at 

 the close of the last century, given amounts of various commodities 

 which it took a thousand hours of hand labor to produce under the 

 conditions that prevailed at the close of the Civil War. At the pres- 

 ent time every process has been improved so much, especially under 

 the pressure of the Great War, that the figures in the last column 

 may be reduced by one half or more in most cases. 



COST IN HUMAN HOURS OF PRODUCING BY MACHINERY 

 THE EQUIVALENT OF 1000 HOURS OF HAND WORK 



Units OF Value Hours Units of Value Hours 



Barley, 470 bu. .... 42.4 Books (binding), 2190 vols. 263.4 



Corn, 22obu. . ." . . i5i-3 Shoes, 45 pr i35-o 



Oats, 606 bu 107.5 Newspapers, 1,750,000 pages 4.8 



Potatoes, 2000 bu. . . . 345-3 Envelopes, 230,000 . . . 72.6 



Wheat, 310 bu 46.0 Granite (dressing), 6150 sq. ft. 77.9 



