Anonymous examples are sufficient to elucidate principles, if not to establish them; and elucidation is often the sole purpose for which an example is needed.

Retrospective elucidations are valueless and sometimes irritating.

The bearing of the conclusions which are now either established, or highly probable, respecting the origin of silicious, calcareous, and clayey rocks, and their metamorphic derivatives, upon the archaeology of the earth, the elucidation of which is the ultimate object of the geologist, is of no small importance.