Graduation. - All plans are now being graduated in skeleton style before publication in order to facilitate easy reference to Astronomical
positions; previously published plans are also graduated as opportunity offers. The graduation is, however, of necessity, often based upon
imperfect information of a conflicting nature; for this reason, whenever an Astronomical position is quoted other than approximate (i.e. when
seconds are given), it is necessary to quote also the number of the particuar chart from which the position has been derived.