using both circles is *60' / 30 *or 2 minutes. There are several ways to read the minute value using both

circles. These additional values are demonstrated and explained in the following examples:

upper circle is to the right of that of the lower circle, the value is *10 + (6 graduations x 2')*, which is

equal to *10 + 12' *(Figure 3-9).

When the correct or true value for the degrees does not show in the circle telescope, the reading for the

minute value can be made in either of the following two ways.

minute value must be subtracted from the visible degree value to give the true value of the direction.

Therefore, *10 - (9 graduations x 2*') is equal *to 10 - 18'*, which is equal to *9 42'.*

Count to the right the number of divisions from the true degree value on the lower circle (which does not

show) to the value 190, difference on the upper circle. Realizing that from the 9, mark to the 10 mark

on the lower circle there are 15 divisions, count the number of divisions to the right from the 10, mark

on the lower circle to the 189 mark on the upper circle.

(4) The previously described methods, using both circles, are slower than methods using the

index mark. However, it is also possible for the index mark to be