TEXTBOOK OF LANDSCAPE GARDENING 
For practice purposes it will be found effective to have a number 
of lines laid out, their true compass bearings being known to the 
teacher but not to the pupils. The pupils should then read these 
bearings repeatedly and with all the different makes of compasses 
available. After thirty or forty readings, which should be recorded, 
the pupil will see how accurate is his work. He should observe 
his average error and his limit of error. After one day of attentive 
practice the student, using any fairly good instrument, should re- 
duce his average error to 2° and his extreme error to 5°. 
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