MATERIALS FROM PLANTS AND ANIMALS 419 



it is not astonishing that the same materials should be to some 

 extent usable for both. Timber is perhaps the most widely 

 used building material ; its use ranges from the log cabin of the 

 pioneer to the highly finished woodwork of modern city dwell- 

 ings. Where there are no large trees other plant material may 

 be available, as the bamboos used in parts of China, Japan, and 

 India. The thatch of roofs still used in many parts of Europe 

 and Asia is supplied chiefly by the stalks or straw of plants of 

 the grass family or by leaves and husks. In buildings constructed 

 of stone and steel, or of other mineral matter such as brick and 

 concrete, organic matter is of value to prevent too rapid changes 

 in temperature. For this purpose wooden finish is used on the 

 inside, or various composition boards in which wood fiber forms 

 an important part. In the same way prepared papers are often 

 used in the walls, under the floors, and under the roofs of houses. 

 Animal materials are very seldom used in building houses, but 

 to some extent cow hair is still used as a binder in the making of 

 mortar. 



Occasionally peat has been used as a building material. Peat 

 is a mass of earth in which there is a large proportion of decay- 

 ing vegetable matter ; it can therefore also be used as fuel. It 

 is found in bogs, and at certain seasons of the year it may be 

 cut out in rectangular blocks and allowed to dry in the sun. It 

 is believed that peat represents the early stages in the process of 

 coal formation. 



The problem of shelter includes, of course, that of maintain- 

 ing protection from the cold ; and that suggests fuel. Most of 

 the fuel that we use is obtained directly from wood ; nearly all 

 the rest indirectly, for when we burn coal we are using the car- 

 bon deposited millions of years ago in trees long dead, and when 

 we burn oil or gasoline or kerosenes we are using the products 

 of chemical change in plants of past ages. Alcohol as a fuel can 

 be produced also from wood and other vegetable matter, al- 

 though the tendency is to get more and more of it from the 

 waste products of industries in which vegetable material is used 

 — molasses from sugar refineries, for example. 



