ABSTRACT
How networks appear in the real world, and how they can be studied with a reasonable mixture of mathematics and observations.
One of the greatest consolations of this world is friendship, and one of the pleasures of friendship is to have someone to whom we may entrust a secret. Now, friends are not divided into pairs, as husband and wife: everybody generally speaking, has more than one; and this forms a chain of which no one can find the first link. When, then, a friend meets with an opportunity of depositing a secret in the breast of another, he, in his turn, seeks to share in the same pleasure. He is entreated, to be sure, to say nothing to anybody; and such a condition, if taken in the strict sense of the words, would immediately cut short the chain of these gratifications: but general practice has determined that it only forbids the entrusting of the secret to everybody except one equally confidential friend, imposing upon him, of course, the same conditions. Thus, from confidential friend to confidential friend, the secret threads its way along this immense chain, until, at last, it reaches the ear of him or them whom the first speaker exactly intended it should never reach. However, it would, generally, take a long time on the way, if everybody had but two friends, the one who tells him, and the one to whom he repeats it with the injunction of silence. But there are some highly favoured men who reckon these blessings by the hundred, and when the secret comes into the hands of one of these, the circles multiply so rapidly that it is no longer possible to pursue them.1
