Mercantile bills are an exceedingly difficult kind of security to understand.

The relative credit of different merchants is a great 'tradition'; it is a large mass of most valuable knowledge which has never been described in books and is probably incapable of being so described.

The subject matter of it, too, is shifting and changing daily; an accurate representation of the trustworthiness of houses at the beginning of a year might easily be a most fatal representation at the end of it.
In all years there are great changes; some houses rise a good deal and some fall.

And in some particular years the changes are immense; in years like 1871 many active men make so much money that at the end of the year they are worthy of altogether greater credit than anyone would have dreamed of giving to them at the beginning.

On the other hand, in years like 1866 a contagious ruin destroys the trustworthiness of very many firms and persons, and often, especially, of many who stood highest immediately before.