But some of the most singular appearances of the sea and sky in the polar regions are presented in summer. During that season the perpetual presence of the sun and the large tracts of ice floating about on the sea exert their opposing influences so as to produce the most astonishing results. One part of the sea being covered with ice, produces a cold atmosphere; another part being free from ice, produces a warmer atmosphere. Refraction is the result of viewing objects through those different media, and very curious appearances follow. When Scoresby was in Greenland a singular atmospheric phenomenon occurred, whereby he became aware of the approach of his father's ship some time before it rose above the horizon. He had reached Greenland before his father, who followed him in the _Fame_. The following is his account of the circumstance: "On my return to the ship, about eleven o'clock, the night was beautifully fine and the air quite mild. The atmosphere, in consequence of the warmth, being in a highly refractive state, a great many curious appearances were presented by the land and icebergs. The most extraordinary effect of this state of the atmosphere, however, was the distinct inverted image of a ship in the clear sky, over the middle of the large bay or inlet, the ship itself being entirely beyond the horizon. Appearances of this kind I have before noticed, but the peculiarities of this were the perfection of the image, and the great distance of the vessel that it represented. It was so extremely well defined, that, when examined with a telescope, I could distinguish every sail, the general `rig of the ship,' and its peculiar character; insomuch that I confidently pronounced it to be my father's ship the _Fame_, which it afterwards proved to be, though, on comparing notes with my father, I found that our relative positions at the time gave our distance from one another very nearly thirty miles, being about seventeen miles beyond the horizon, and some leagues beyond the line of direct vision." Scoresby was, perhaps, one of the most persevering and intelligent observers of nature that ever went to the polar seas. His various accounts of what he saw are most interesting. We cannot do better than quote his remarks upon _ice-blink_, that curious appearance of white light on the horizon, whereby voyagers are led to infer the presence of ice:--