How frail and ephemeral is the material substance of...

How frail and ephemeral is the material substance of letters, which makes their very survival so hazardous. Print has a permanence of its own, though it may not be much worth preserving, but a letter! Conveyed by uncertain transportation, over which the sender has no control; committed to a single individual who may be careless or inappreciative; left to the mercy of future generations, of families maybe anxious to suppress the past, of the accidents of removals and house-cleanings, or of mere ignorance. How often it has been by the veriest chance that they have survived at all.