There are four kinds of readers. The first is like the hourglass; and their reading being as the sand, it runs in and runs out, and leaves not a vestige behind. A second is like the sponge, which imbibes everything, and returns it in nearly the same state, only a little dirtier. A third is like a jelly bag, allowing all that is pure to pass away, and retaining only the refuse and dregs. And the fourth is like the slaves in the diamond mines of Golconda, who, casting aside all that is worthless, retain only pure gems.