1906 



FORESTRY AND IRRIGATION 



431 



Bending tests were made upon 

 beams with a span of 13 feet 6 inches 

 and ranging from 4 by 10 by 6 by 12 

 inches in cross-sections. From these 

 tests, showing the strength and stiff- 

 ness of sound green tamarack and 

 Norway pine in structural sizes, the 

 results were as follows : 



Strength (Modulus of rupture 

 Tamarck, 4,600 pounds per square 

 inch ; Norway pine, 4,000 pounds per 

 square inch. 



Stiffness (Modulus of elasticity) 

 Tamarack, 1,240,000 pounds per 

 square inch; Norway pine, 1,189,000 

 pounds per square inch. 



Green tamarack thus appears to be 

 uniformly stronger and stiffer than 

 green Norway pine. When over-dry 

 tamarack weighs twenty-nine pounds 

 per cubic foot and Norway pine about 

 twenty-four pounds per cubic foot. 



Tamarack is usually of slower 

 growth than the pine. Bending tests 

 on small clear pieces indicate that 

 strength decreases in tamarack when 

 the rate of growth is faster than an 

 inch in eight years, and in Norway 

 pine when the growth is faster than 

 an inch in ten years. Comparative 

 tests on the seasoned timber of the 

 two species will be made later. 



Change of 

 Boundaries 



The boundaries of the 

 Grand Canyon Forest 

 Reserve, Arizona, have 

 been changed by the exclusion from 

 the reserve of a tract twelve miles 

 long and six miles wide at the ex- 

 treme northern limit of the reserve. 

 Whereas the north boundary of the re- 

 serve formerly touched the Utah State 

 line, it is now six miles south of it. 

 At the same time a slight addition has 

 been made to the reserve consisting of 

 a narrow strip of land along the north- 

 ern portion of the eastern boundary. 

 This tract, twelve miles long and aver- 

 aging little more than a mile in width, 

 has been added to bring the reserve 

 boundary out to the base of the moun- 

 tains, where it can be readily located 

 by the stockmen. The original bound- 

 ary ran about two miles back from the 

 base of the mountain, where it could 



not be seen except by the merest 

 chance. 



In the area recommended for exclu- 

 sion there is no timber of value. The 

 forest growth is of inferior pinon and 

 mountain mahogany. The region is 

 entirely without water, so that it is 

 impossible to keep a patrol or to main- 

 tain range headquarters. Yet it con- 

 tains the main highway to either side 

 of the range. By its exclusion from 

 the reserve, stock may be crossed at 

 will, without any restrictions upon 

 those who are compelled to use this 

 highway, who would be under con- 

 siderable inconvenience and difficulty 

 in visiting forest officers for permits. 



As the reserve now stands its area 

 is 2,267,300 acres. 



Holding The Forest Service has 



^d e s4e S ail " completed a series of 

 pi e tests to determine the 

 holding power of different forms of 

 railroad spikes. The tests were made 

 on ordinary commercial ties of lob- 

 lolly pine, oak, chestnut, and other 

 woods. The spikes used were of four 

 kinds common driven spikes, a 

 driven spike which has about the same 

 form as the common spike with a 

 lengthwise channel on the side away 

 from the rail ; screw spikes of the 

 American type, and screw spikes simi- 

 lar to those in use on European rail- 

 roads, and differing from the Ameri- 

 can spike mainly in the manner of 

 finishing the thread under the head. 



The common and the channeled 

 spikes were driven into the ties in the 

 usual manner to a depth of five inches. 

 A hole of the same diameter as the 

 spike at the base of the thread was 

 bored for the screw spikes, which were 

 then screwed down to the same depth 

 as the driven spikes. The ties were 

 then placed in the testing machine and 

 the force required to pull each spike 

 was recorded. 



The average force required to pull 

 common spikes varies from 7,000 

 pounds in white oak, to 3,600 pounds 

 in loblolly pine, and 3,000 pounds in 

 chestnut. The holding power of the 

 channeled spike is somewhat greater. 



