TEXTBOOK OF LANDSCAPE GARDENING 
There are several methods of numbering the graduations of 
the dial. The two methods most often used are: 
1. Quadrant Graduation with a zero at both the north and 
south, the numbering increasing in each direction up to 90 degrees 
at both east and west. Quadrant courses are recorded by their 
relation to the N.-S. line as N. 10° E. or S. 77° W. ete. 
This is the usual form of graduation of the box compass and is 
the one most often used by land surveyors. It is liable to give rise 
to confusion and error as there are four different courses for every 
degree number as N. 10° E., N. 10° W., S. 10° E., S. 10° W., two of 
the courses being the reverse directions of the other two. 
2. Azimuth Graduations: In this form there is but one zero 
which is at the north, the degrees being numbered continuously to 
the right (clockwise) through E., S. and W. to 360° which coin- 
cides with zero at the north. 
There is thus but one course for any degree number and there- 
fore less chance for confusion in reading or recording. This is the 
usual graduation of the prismatic compass. 
Important Note: The actual numbering on a floating dial 
usually starts with zero at the south and runs clockwise but as the 
reading is always made at the rear end of the sighted line in the 
prismatic compass this arrangement of the numbering gives correct 
readings based on zero at the north. 
It should be carefully noted that with the floating dial we read 
the direction on the line of the course while with a fixed dial we read 
the direction not on the line of the course but at the N. end of the 
needle. 
The course is the line through the sight vanes, or if there are 
no vanes it is along the N.—S. line of the dial which line is brought 
to bear on the object whose direction is sought. 
When the dial floats it brings the reading to the sighted line. 
When the dial is fixed the instrument revolves about the needle which 
maintains a constant N.-—S. position and the course is shown by the 
angular distance between it and the N.-S. line of the dial as read 
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