A. First. The fore, middle, and ring-fingers of the right hand taken in that order.
B. Second. The fore, middle, and ring-fingers of the left hand taken in that order.
C. Third. The thumb and little finger of the right hand.
D. Fourth. The thumb and little finger of the left hand.
Consequently an index-heading will be of the form—
| First group. | Second group. | Third group. | Fourth group. | |||
| a a l | a a w | l l | l l |
These index-headings are catalogued in alphabetical order. The method used in the Index is that which takes note of no slopes, except those of loops in the fore-finger of either hand. Consequently the index-heading for my own digits, printed on the title-page, is wlw oll wl wl. Those of the eight sets in [Plate VI.] are as follows:—
| i l w | i l l | w w | w l | |||
| o l w | o l w | w l | l l | |||
| o l w | o l w | w l | l l | |||
| o l w | o l l | l l | l l | |||
| i l w | i l w | w l | w l | |||
| i l w | i w l | l l | l l | |||
| i l l | w w l | l l | l l | |||
| o l l | a a l | l l | a l | |||
| o a a | a a a | l a | l a |
For convenience of description and reference, the successive entries in the specimen index have been numbered from 1 to 100, but that is no part of the system: those figures would be replaced in a real index by names and addresses.
A preliminary way of obtaining an idea of the differentiating power of an index is to count the number of the different headings that are required to classify a specified number of cases. A table is appended which shows the numbers of the headings in the three alternative methods (1) of noting slopes of all kinds in all digits, (2) of noting slopes of Loops only and in the fore-fingers only, and (3) of disregarding the slopes altogether. Also in each of these three cases taking account of—