FORESTRY. 215 



What is the amount of the annual expenditure for rail- 

 road ties ? 



773. From an average tree three railroad ties may be 

 cut. How many trees are annually required to furnish 

 the needs of the railroads for replacing the old ties, the 

 average life of a tie being six years ? 



774. A certain railroad uses annually 3,840,000 rail- 

 road ties. If three ties may be cut from a locust tree 30 

 years old, how many acres will be required to be planted 

 each year, 400 trees being planted per acre, to furnish 

 the supply? 



775. What is the total number of acres in trees re- 

 quired to supply the needs of this railroad ? 



776. How many trees, from one to 30 years old, must 

 be growing to keep the needs constantly supplied? 



777. How much is an acre of locust trees worth, three 

 ties to each tree, 400 trees to an acre, when sold at 30 

 cents a tie ? 



778. A farmer wishes to renew the sills of his barn, 

 and finds that he must have 12 pieces, 10 inches by 6 

 inches, white oak timber and 25 feet long. How many 

 board feet is this equivalent to (a board foot is equivalent 

 to a piece of 12 x 12 x 1 inch), and what will be the cost 

 at 4 cents a board foot? 



779. If 60 board feet of sawed lumber, also worth 4 

 cents per board foot, can be obtained from a tree in addi- 

 tion to one sill, and a half cord of firewood, worth $4 

 a cord, what is the total value of the tree's product? 



780. If an acre contains ten such trees, and in addi- 

 tion 40 other trees fit for cord wood with an average 



