PLANT COVERING OF THE EARTH. 167 



wood. So, too, timber is necessary for the con- 

 struction of our agricultural machinery, of the 

 greater part of our ships, and of a host of other 

 structures which are essential to the well-being 

 of man. In the present state of our arts, we 

 could more easily give up all the other resources 

 drawn from the earth, except perhaps iron, than 

 forego the use of wood from our civilization. 



Although mineral coal has, in the more civilized 

 parts of the world, to a great extent taken the place 

 of wood for heating purposes, probably three-fourths 

 of the domestic hearths in the world are supplied 

 from the forests. In time it is to be hoped that 

 the use of stone coal will become yet more exten- 

 sive, for it will diminish the tax which is made 

 upon the woods, and so spare them for more 

 necessary uses. 



Among the uses of the forests we must include 

 the shelter which they afford to human beings, and 

 to the cattle of our farms. Where the country is 

 untimbered, the winds, having a free sweep over 

 the surface of the earth, move in times of storm 

 more furiously than in the forests, where the trees 

 afford a most important shelter. In the prairie 

 districts of the upper Mississippi, it has been found 

 necessary to plant trees about the homesteads in 



