Caption:

Colour engraving by Josiah Wood Whymper taken from 'Phenomena of Nature', published in London in 1849 for the Society for Promoting Christian Knowledge. 'Sea water requires a much greater degree of cold to freeze it than fresh water, and the motion of the waves interferes with the formation of solid ice. Under certain conditions, however, 'fields' of ice can be formed, often extending to a distance of several hundred square miles. When warmer weather prevails, these fields can be broken into smaller pieces of ice which are called 'floes'.'