Meteorology: the sun in Baffin Bay disperses thick fog in the shape of a semicircle. Coloured etching by P. Fumagalli, 1827, after B. O'Reilly.

A phenomenon observed by Bernard O'Reilly on his expedition in 1817 to Greenland: "A luminous arch appeared this afternoon in opposition to the sun, but destitute of iridescence: the whole interior of this arch was strongly luminous, and objects within its compass partook of that illumination: I thought it worthy of a place among the sketches, as not having been heretofore noticed in any publication within my experience"--O'Reilly, op. cit. p. 196. In the foreground are seals or walruses