“A common slave (you know him well by sight) Held up his left hand, which did flame, and burn Like twenty torches join’d; and yet his hand, Not sensible of fire, remained unscorched....  And, yesterday, the bird of night did sit, Even at noon-day, upon the market-place, Hooting and shrieking.  When these prodigies Do so conjointly meet, let not men say, ’These are their reasons—­they are natural; For, I believe, they are portentous things.”

A great many others besides our good Casca believe in these portents and signs, and their dignity would be much hurt if they were persuaded that the world would go on just the same if they and their family were utterly extinct, and that no eclipse would happen to portend that calamity.  In Ireland, in certain great families, a Banshee, or a Benshee, for they differ who spell it, sits and wails all night when the head of the family is about to stretch his feet towards the dim portals of the dead; and in England are many families who, by some unknown means, retain a ghost which walks up and down a terrace, as it did in that fanciful habitation of Sir Leicester Dedlock.  In Scotland, they have amongst them prophetic shepherds, who, on the cold, misty mountain top, at eventide, shade their shaggy eyebrows with their hands, and, peering into the twilight, see funerals pass by, and the decease of some neighbor portended by all the paraphernalia of death.

With us all these portents “live no longer in the faith of Reason;” we assert, in Casca’s words, that “they are natural;” but we offend the credulous when we do so.  “Illusions of the senses,” says an acute writer, “are common in our appreciation of form, distance, color, and motion; and also from a lack of comprehension of the physical powers of Nature, in the production of images of distinct objects.  A stick in the water appears bent or broken; the square tower at the distance looks round; distant objects appear to move when we are in motion; the heavenly bodies appear to revolve round the earth.”  And yet we know that all these appearances are mere illusions.  At the top of a mountain in Ireland, with our back to the sun, we, two travelers, were looking at the smiling landscape gilded by the sunshine; suddenly a white cloud descended between us and the valley, and there upon it were our two shadows, distorted, gigantic, threatening or supplicatory, as we chose to move and make them.  Here was an exactly similar apparition to the Specter of the Brocken.  The untaught German taxed his wits to make the thing a ghost; but the philosopher took off his hat and bowed to it, and the shadow returned the salute; and so with the Fata Morgana, and the mirage.  We now know that these things had no supernatural origin, but are simply due to the ordinary laws of atmospheric influence and light; so all our modern illusions are easily rectified by the judgment, and are fleeting and transitory in the minds of the sane.