494 Introduction to the Study of Science 



mendous size and weight, which they transported on some sort 

 of a sledge to the river and then on barges to their destination. 

 The two giant statues of the Pharaohs at Thebes were each 

 carved from a single block of stone weighing as much as one 

 thousand tons. Probably the common people of the valley 

 dwelt in adobe houses similar to those in the southwestern 

 section of the United States. The Chaldeans and Babylonians 

 made use of clay brick in most of their buildings. Are any of 

 their structures standing to-day ? Of what materials were the 

 Greek and Roman public buildings, bridges, and homes con- 

 structed? Why were such materials used? What materials 

 utilized by ancient builders proved most durable? 



Properties of building materials. A hasty survey of the 

 building materials utilized in the past suggests that a perfectly 

 satisfactory material for building must be abundant, easily 

 obtained, readily shaped or adapted to the use or design, durable, 

 fire-resistant, a good non-conductor of heat, practically im- 

 pervious to water, and not liable to crack and crumble with 

 changes from wet to dry or from cold to hot weather. Is there 

 any material which meets all these requirements ? 



Exercise. What qualities do trees and lumber possess ? What 

 properties are found in brick or other clay products for building pur- 

 poses? What are the properties of stone, iron and steel, and concrete? 



What are the chief differences between the requirements of build- 

 ing materials for large cities and those for villages or rural buildings ? 

 What are the principal reasons for the differences? Consider in your 

 answers the factors of fire, collapse, and decay. 



I. WOOD 



189. Properties and use. In the United States more wood 

 is used at present for building than any other material. What 

 are the reasons for this? What change in regard to the use of 

 wood for building is being made in cities ? What are the reasons 

 for such a change ? Make a list of the building materials used 

 in your community, noting especially the following points: 



