On a clear day in April, onlookers standing in Mt. Hope Cemetery were  met with an astounding sight: Canada. This was the Rochester Mirage of  1871. Normally 400 feet below the horizon, the shore on the other side  of Lake Ontario loomed closer than ever, with the lake itself seeming to  have engulfed the northernmost half of our city. Or so the story goes.  But what actually happened? And what can the Mirage tell us about the  Rochester of that time, and about history as a whole?