SECOND GRADE SPRING WORK 109 



many acres of our forest trees. How are they often started ? 

 Sheep will gnaw and eat the bark from the stems of young 

 trees and kill them. In what other ways may forests be 

 injured by means of carelessness or ignorance? 



The government is trying to get the people to plant small 

 forest trees on all waste lands so that we shall not run out of 

 wood. Many of our forests are now protected by the govern- 

 ment to prevent their destruction by fire, large herds of animals, 

 or by waste of any kind. Such areas are called Forest Reserves 

 or National Forests, and officers continually guard them. 



How long does it take for a tree to grow until it is big 

 enough for lumber? How can you tell? Count the rings 

 or the grain in a board, and form an estimate. Already the 

 kind of cedar used in making lead pencils is nearly gone and 

 the manufacturers hardly know what they are going to do. 

 Substitutes for wood are being used in many places. Pen- 

 cils are covered with paper. Wharves and piers which re- 

 quire great quantities of lumber are now being made of 

 asphaltum, and bridges and supports in buildings, formerly 

 made of heavy timbers, are now made of cement. 



LESSON XXXII 

 THE SENSE OF SIGHT 



What light rules the day? What light rules the night? 

 When can we see better ? Why ? What do we do to aid our 

 sight at night ? We see things because light from them comes 

 into our eyes. The little black spot in our eyes is a sort of 

 window which lets in the light. You can see it grow large 

 or small as you remove the light or bring it close to another's 

 eye. It is a self-regulating window. 



