The soil of yards and the floors and walls of houses rapidly become contaminated, and the ideal condition would be to have an impermeable flooring covering the whole area, and supplied with suitable layers of sand, sawdust, peat-moss or other absorbent substances which can be changed at frequent intervals.
Peat-moss of the most sterile character has been by this process covered with soil of the greatest fertility, and swamps which used to be resorted to for leeches are now, by the effects of warping, converted into firm and fertile fields.
The thick peat moss or tundra of the undrained lowlands covers probably at least a quarter of Alaska; the ' The trees here grow as large as 10 in.
The timber resources of Alaska are untouched 2 280 species of mosses proper, of which 46 were new to science, and 16 varieties of peat moss (Sphagnum) were listed by the Harriman expedition; and 74 species or varieties of ferns.
A mulch of grass clippings or peat moss will also protect the tree from loss of water in dry weather.
