‘ THE LUMBER INDUSTRY 157 
In many places where wood is scarce, houses are 
constructed of mud or sods. Cow dung is often dried 
for fuel even in Germany, and only a few years ago 
corn was used for fuel in place of wood in Kansas. 
The great value of wood is due to its beauty and 
variety, and to the fact that it can be easily worked 
with tools, and easily held in place with nails and 
glue. A very important feature of timber is the man- 
ner in which it conducts itself toward nails. Some 
timbers split easily when nailed, while others hold 
nails tenaciously. One of the virtues of hemlock 
timber is the way in which it grasps nails. <A nail 
holds a board fast, but the firmness with which it 
holds it depends upon the firmness with which the 
wood holds the nail. Some woods are valuable be- 
cause they prevent nails from rusting. A nail never 
rusts in teak-wood. 
The early settlers of this country were armed 
with a mighty weapon and implement. It was the 
iron ax, by means of which the primeval woods were 
conquered. The American ax has been improved by 
many Yankee inventions until it is now the finest ax 
of all the world. Its development has been aided by 
the presence of hickory for handles. The genus 
Hickoria is peculiar to North America. 
Soon ships were built and sawmills constructed 
along the streams, and lumber was exported to vari- 
