Colour engraving by Whymper from 'Phenomena of Nature', published in London in 1849 for the Society for Promoting Christian Knowledge. 'Some central parts of North America are occupied by vast plains known as 'prairies'. This vast crop of gras, having ripened its seed, dies and is converted by the heat of the sun into a dry and inflammable mas. In Autumn or early in the Spring, it frequently catches fire and the progres of the flames is not arrested except by a river or by heavy rain.'
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