all the examples which have been preserved, and to compare these examples with each other, first as to common features of likeness, secondly as to features of unlikeness. By this process we are able to restore whatever may be really deficient from insufficiency of any particular record—and such a restoration is above all thing essential—and to present for examination not an isolated specimen but a series of specimens, each of which helps to bring back to observation some portion of the original.
The first important characteristic which distinguishes a custom or belief in survival from a custom or belief belonging to an established system is that not only do different examples present points of common likeness, but also points of unlikeness. The points of likeness are used to determine and classify all the examples of one custom or belief, the points of unlikeness to trace out the line of decay inherent in survivals.
This partial equation and partial divergence between different examples of the same custom or belief allows a very important point to be made in the study of survivals. We can estimate the value of the elements which equate in any number of examples, and the value of the elements which diverge; and by noting how these values differ in the various examples we may discover an overlapping of example with example which is of the utmost importance. A certain custom consists, say, of six elements, a, b, c, d, e, f. Another example of the same custom has four of these elements, a, b, c, d, and two divergent elements, g, h. A third example has elements a, b, and divergences g, h, i, k. A further example has none of the elements, but only divergences, g, h, i, l, m. Then the statement of the case is reduced to the following:—
| 1=a, b, c, d, e, f, | ||
| 2=a, b, c, d | +g, h. | |
| 3=a, b | +g, h, i, k. | |
| 4= | +g, h, i, | l, m. |
