The mass of mystery

Middlemarch, book 7, chapter 71:

But this vague conviction of indeterminable guilt, which was enough to keep up much head-shaking and biting innuendo even among substantial professional seniors, had for the general mind all the superior power of mystery over fact.  Everybody liked better to conjecture how the thing was, than simply to know it; for conjecture soon became more confident than knowledge, and had a more liberal allowance for the incompatible. Even the more definite scandal concerning Bulstrode's earlier life was, for some minds, melted into the mass of mystery, as so much lively metal to be poured out in dialogue, and to take such fantastic shapes as heaven pleased.