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In consequence of this preserving effect of peat, it is possible to trace the entire history of a peat-moss from the very beginning. Remains of the Dwarf Willow or Polar Birch have been found in England, showing that those now Arctic plants were then flourishing in Norfolk. These are generally in the lowest layers of peat-mosses. Next follow remains of the Birch and Aspen, which would be growing, as they do in places to-day, on mossy soil where the peat was still thin. Higher up in the peat one finds remains of Scotch Fir, showing that at that time regular forests of Scotch Fir existed, e.g. in Sutherlandshire and on Lochar Moss, where they do not grow at present.