THE DEPENDENCE OF MAN 5 
Animals and plants as sources of shelter. Such of our ances- 
tors as were fortunate enough to inhabit mountain districts lived 
in caves, but as the more venturesome and ambitious sought 
their fortunes on the plains, where civilization develops, they 
made themselves tents or tabernacles of the skins of animals 
and afterward of woven cloth. Only later were shelters built of 
lumber, bricks, or stone. Our own race has developed its civili- 
zation in habitations made of wood, but with the passing of the 
years and the destruction of natural forests, we shall more and 
more build of indestructible materials not the product of either 
plant or animal life. , 
For our furniture and our furnishings, however, we shall 
always be dependent upon both, and we cannot say, even in 
this, that man is independent of the humbler life about him. 
Though in the past his draft for building materials has been 
upon natural supplies and not upon domesticated races, yet the 
attention that is now being given to forestry indicates the neces- 
sity of protecting and renewing the timber supplies in ways that 
amount almost to a domestication of our valuable woods. 
Vegetable products as sources of heat and light. For ages 
wood has warmed the body of suffering man, cooked his food, 
and lifted the shadows from his soul. Not until after the open- 
~ ing of the twelfth century! did we begin to draw upon our coal 
deposits, and not until recent years have petroleum and natural 
gas ranked as heat- and light-producing materials. 
‘But whether wood or coal, petroleum or gas, all reduce to the 
same ultimate basis, — vegetable growth and the carbon of the 
atmosphere harnessed by the green of the leaf operating under 
the energy of the sun. 
None of these sources of heat is from cultivated plants, but 
the world supply of coal, and therefore of petroleum and gas, is 
limited, so that at no distant day we shall be obliged to secure 
our heat either from the sun direct, from wood growing in 
1Jt is supposed that the first charter for mining coal was granted by 
Henry III to Newcastle-on-Tyne, 1239. 
